Studio Demo Project

August 15, 2012 by Leave a Comment

Recording Studio Issues

Most of the recording studios in Arizona have some type of acoustical issue in their drum, voice, and control room. Most of the time it is low frequency issues, but excess reflections from room boundary surfaces produces reverberation times that come in a close second for concern. All studio owners know the issues in each room of their studio. Some know what to do, but most know they have to do something but need some assistance with this process.

Bass, Mids, Highs

The two major areas are bass absorption and middle and high frequency absorption to manage reflections and lower reverberation times. We can use low frequency absorption to manage bass energy in our room. The optimum word here is manage. Bass energy really is never controlled. We can use absorption and diffusion to minimize reflections and actually control rates and levels and bring this number in line with some predetermined scale of sonic acceptance.

Acoustic Foams / Quadratic Diffusion

Absorption materials are many but acoustic, open celled, foam is a very cost effective way to achieve a lot of middle and high frequency absorption in a small depth space. Diffusion can also be used but most studio owners have heard of it but never used it. This uncertainty usually means they will be too busy to try it let alone buy it. However, if it is in the studio over a certain time period, it will get used at some point. If the tools are in the tool box, a sound situation will arise in the studio where the tools will be needed.

Demo Studio Kit

To remedy this situation, I have assembled a demo kit if you will of low frequency absorbers, foam, and quadratic diffusion to assist studio owners in the Arizona area. I take the units to a local studio that has agreed to use them for a 30 day period. This “bag of tools” can go a long way to further the understanding for studio owners of what type of technology will work best for their particular studio issues.

From back to front: Quadratic diffusors, acoustic foam technology, bass absorbers

Acoustic Foam

Acoustic foam is a cost effective way to manage reflections and reverberation times. One must choose the acoustic foam that meets the rates of absorption that fits musical presentation in our control rooms. In a monitoring environment, we must be careful not to use too much absorption.

It can not be just any level of absorption. We don’t need to absorb 100 % of everything at all frequencies. We need gentle, sound absorption absorption rates, so that the life of the energy we are absorbing is not destroyed. We do not want to be sonic vampires and suck the life out of our musical energy. For one thing, every watt of energy costs a lot to produce they way we want it because of equipment and room costs.

Quadratic Diffusion

Diffusion and particularly quadratic diffusion can spread room boundary reflections out and reduce their impact at our monitoring position. A vertically positioned diffusor spreads sound energy that enters it out in a horizontal, fan like array and lessens the reflections impact at our monitoring position. A horizontally positioned diffusor will spread sound energy out in a vertical fan like array. These two diffusors now are
producing two dimensions of sound diffusion.

More Air

Diffusion can minimize reflections and make our rooms sound larger than they are. Reflections from our room boundary surfaces can flood our listening positions and create confusion that our brains will have difficulty localizing. Diffusion can minimize those effects and spread out those reflections into smaller less noticeable ones. Diffusion can breath life into our rooms and add “air” to our presentations.

Low Frequency Issues

Low frequency management plagues almost all studios in some form or another. Today’s smaller rooms produce larger bass issues. One must make every effort to minimize the mix destructive impact of low frequency energy. Resonant pockets of energy must be dealt with in an effective manner that really has an amplitude impact on the resonance. Don’t make the mistake of looking to foam for a low frequency energy absorber.

Diaphragmatic Absorption

A powerful, low frequency, absorbing technology is termed diaphragmatic absorption. It is a sealed unit, with a front wall that acts a diaphragm. The diaphragm reacts to sound pressure, especially low frequency sound pressure, and slows the low frequency energy down before it enters the inside of the diaphragmatic absorber. Once inside, it must go through the cabinet’s middle fill material. If one chooses the correct cabinet fill material, you can achieve rates and levels of absorption that are necessary to deal with today’s small room pressure areas.

High Pressure Performer

Diaphragmatic absorption works best in room areas of highest sound pressure. It works best close to speakers and sub woofers that produce this pressure. They work best in room positions of higher pressure. Room corners and room boundary intersections along our baseboards and wall/ceiling intersections are good places. One must be able to use the appropriate diaphragm for the area of pressure we are addressing.

Sound Pressure Area Specific

If our area of pressure is high like around our speakers, we must use a diaphragm that will move with this high pressure area. It is the movement of the diaphragm that creates the absorption results. Lower pressure areas need thinner diaphragms to encourage as much movement as possible with the given pressure levels. High pressure areas need thicker diaphragms or multiple diaphragms to create the rates and levels of necessary sound absorption.

Reflection management from our room boundary surfaces at our monitoring position, diffusion technology for the rear wall of our monitoring rooms to deuce rear wall slap at the monitoring position, and always in almost any room, the need for low frequency management. Not any type of low frequency absorption, definitely not acoustic open celled foam, but the use of diaphragmatic absorption placed at the proper pressure areas will provide the necessary rates and levels of real low frequency absorption that only occurs below 100 cycles. Rates and levels of absorption that can make a sonic impact on the attack and decay of our individual bass notes.

Filed Under: Environmental Building, Room Acoustics Tagged With:

Room Acoustics: Science and Art

May 16, 2012 by Leave a Comment

Room Sound

It is amazing to me that each room we go into has a different “sound” to it. Some rooms (most) have a lot of bass energy. Some have low reverberation times, some high. Sound stage presence ranges from small to not so small. Individual vocals and instruments can be heard or smothered in a comb filtered bath. Room sound seems to vary with the personality of the room user, the personality of the room, and the room’s use objective. We must use science to assist us with low frequency resonances and their associated harmonics within our rooms.

Bass Energy

Bass energy or low frequency control in our rooms is a constant and predictable sonic threat unless we have at least a single room dimension of 30′. Two room dimensions of 30′ is even better. No one has that. Therefore, we are all faced with managing low frequency issues within our rooms. We must manage because low frequency energy issues in our rooms is like having a chronic disease. You will never be completely cured, but science can help you manage it and keep it under control, so it does not interfere with the chosen room use. Low frequencies blurring and smearing our mixes in the recording process are as unwanted as “bass boom” in our home theater and listening room environments.

Bass Control

How to control bass energy issues is another story. First, a clear and concise definition of low frequency is required. A lot of companies who build acoustical products use the label low frequency or bass absorber too freely. Most room “bass absorbers” do not really absorb bass, at least bass in terms of the frequencies that cause real acoustical issues in small rooms. In fact, the term “bass absorber” is a misnomer all by itself. Absorbers do not really absorb bass in the total sense the name implies. They absorb at different rates and levels depending on the low frequency targeted and some do way better than others at this task. Lets use a definition that says bass energy and the room problems it creates is any energy below 100 cycles. This is a good frequency break point since frequency issues above 100 Hz. can be easily managed with current available absorption technology that is consistent and predictable. Frequencies below 100 Hz. are much more difficult and require specific design criteria to accomplish.

Individuals using most of the rooms we have been in have resigned themselves to the “fact” that this is the way bass sounds in every room. Bass is always bad and we just should get used to it because that is the way it is in smaller rooms. This has been their experience and their experience tells them that bass in a room is always like what they now hear with all the resonances accompanied by the blurring and smearing of vocals and instruments. It is not good but we just have to live with it, work around it, or try to ignore it. This is the thinking.

Make The Room Smaller

Most rooms are bass heavy and the individuals who are listening or working in the room have accepted that small rooms are bad for bass. They are but one can reduce resonance enough, not eliminate, so that there is a more clear and defined bass energy presentation to the room. You do not do this by making the room larger (wish), but rather, by making it smaller. You must make it smaller using that proven and time tested method of real, low frequency absorption, namely diaphragmatic absorption. It must be built with using as low of a resonant frequency for the absorber as the room exhibits resonances and having at least 14″ – 16″ of space to work with. It will be heavy, but it will provide a rate and level of absorption that will let other energy come through uninhibited. Bass can be managed, so that it gets out of its own way.

Mids and Highs

Middle and high frequencies within our rooms are another facet of this science / art blend lacing itself through room acoustic science. You can go into a professional recording studio and listen, please listen at same pressure level, and hear one type of room sound. Lets just call room sound the sound from the speakers and the room all mixed together. Go to another recording studio down the street, different sound completely, not even close no matter what listened to pressure level.

Best Sound At Show

Home theater or listening rooms are the same. Go to a audio trade show where they have different speaker and amplifiers set up in basically the same size rooms because they are really all hotel rooms with furniture removed. Well, not all furniture has been removed. Listen to the same equipment type. Listen to just tube amplifiers and solid state amplifiers. Listen to how different each room sounds with basically the same equipment in it from same size room to same size room. Listen to the same size speakers in each room. Most exhibitors will tell you that they are going to win best sound at show.

Both professional and consumers think their art sounds good to them and I am glad it does because you want to work and play in an environment that sounds good to you, not the other way around. However, better sound is there in your room. One can have it and stay in the same room. It just takes a little acoustical effort especially with the low frequency energy in the room. Diaphragmatic absorption will manage excess low frequency pressure issues. Middle and high frequency absorption is available for those problematic frequencies above 100 Hz. We even have diffusion which can be spread out in both horizontal and vertical planes to provide us with two dimensions of diffusion in our rooms. Use diaphragmatic absorption to cover the resonances in the room and then use absorption/diffusion to inject “air” into your sonic presentation.

Filed Under: Environmental Building, Room Acoustics, Uncategorized

The Building Of A PLE With A Living Roof

May 10, 2012 by Leave a Comment

Building a listening room from scratch or as they say in the construction business from the “ground up” is the best way to eliminate any acoustical issues from the drawing phase through the build out. The most important single variable in the drawing phase is the room’s dimensions. Choosing the correct room dimensions from the beginning will save time and money as we go through the project and at the room’s finish. The correct room surface boundary distances and the total room volume can give us a room that requires little or none low frequency issues. And low frequency energy and the resonances they produce in our rooms is and always will be our largest acoustical issue.

How We Picked The Size

What is a best room size? First, we must decide on the end use of the room. For the living roof project, the individual wanted a frequency response that was flat from 20 Hz. – 20,000 Hz. for home theater playback. To achieve this, we have an ideal set of measurements: 30′ W  x 50′ L. To be absolutely sure we have a flat response at 20Hz., we really need  to have a room dimension of 56 1/2′.  This allows a twenty cycle wave to run full cycle and term. We don’t need to use 1/2 wavelength theory when we have 56 1/2′. Our friend decided that he had room for a 50′ room length. At 50′, we are flat down to 22.6 Hz. Everyone on the project was happy. How about the room width?

We need at least 30′ in our width to apply half wave theory, so we get down flat to 20 Hz. at least in theory. Not applying half wavelength theory, we can get down to 37.7 Hz. The site that was chosen allowed for us  a maximum foot print of a 25′ width. This gives us a full length wave run of  45 Hz.  We decided on the 25″ width because of lot size limitations, knowing if we needed to, we could treat the inside of the room with built in activated carbon low frequency absorption at the room’s pressure areas. We all decided that adding any low frequency absorption to the room, we would look  to the floor and wall construction to build it into since our room size and volume was on our side.

Eight inch thick poured concrete walls.

Noise Control

Sound isolation technology just fell into place. The vertical load bearing requirements  for the roof needed a certain structural mass for support of the living roof’s very heavy, 18″ of top soil. Structurally, we needed load bearing support  all around the perimeter. It just so happened that an 8″ solid poured concrete wall all around would provide the structural support needed at room boundaries for the “living roof”.  An 8″ poured concrete wall gives us a STC, sound transmission class, rating of 56.  Our goal after time noise measurements was an STC of 62 – 65. We were well on our way. With 18″ of top soil eventually on the roof, we could now turn our attention to the four wall surfaces that will influence the internal sound of the home theater room.

Electronics Set Up

The theater will be set up across the 25′ room width. The 50′ length will run past the listening position. Initial screen to viewing area distances are at 17′ – 20′, with all three front channel speakers a minimum 10′ away from  front wall.  Side channel and maybe rear channel speaker locations to be determined later. Three sub woofers will provide, hopefully enough low frequency energy for the room volume. We will use a blend of 12″, 15″, and 18″ sub driver diameters. It will be interesting to hear how different size drivers sound in a room that just by its physical size and volume can handle low frequency waves. We will start with sub woofer positions at mid long wall, mid long wall, and mid rear wall. Each sub woofer will be elevated up to a different height from the floor, starting at 18″ and moving through 40″.

Interior Walls

Each interior wall surface will have to be treated acoustically first to deal with any acoustical anomalies and then secondly to achieve the proper blend and balance of wall reflections with direct sound at the viewing/listening seating. The 25′ width walls will each receive some activated carbon absorbers to compensate for a small amount of resonance at lower frequencies. The 50′ long walls will receive a frame supported 4″ thick MDF surfaced wall. Remember, our room size is 25′ x 50′, so we do not have any real, low frequency, resonance issues. However, since we have gone this far with our room, we should make sure all resonances or possibility of them are dealt with at the beginning.

Ceiling Gone

Since it is a home theater room with a large footprint and 12′ high ceilings, we want a surface treatment that acoustically removes the ceiling from our home theater presentation without calling attention to itself both from appearance and performance. Ceiling room treatment must be not seen or heard. To accomplish this, we all agreed on a blend or balance of quadratic diffusion and absorbing foam technology layer throughout. If we use absorption technology for the side walls, which will give us a defined sound stage, we can afford acoustically to put some air back into the sonic presentation using diffusion technology. We don’t want too much and with the large surface area of this room ceiling, we want absorption to handle some of the excess  diffused energy at the listening position with a surface area that large.

Side Walls: Absorption

Side walls will be treated with sound absorbing foam technology. Two different foam thicknesses will be used throughout the side walls beginning in the front wall corner and extending past the listening position. This will give us a smooth rate and level of side wall absorption at the listening position, so we can control the energy generated from 6 1/2′ speakers. Our goal at the listening position is for more direct sound which is the straight line sound from your speakers to your ears than reflected sound from our room boundary surfaces. We need some reflections to generate spaciousness within the direct sound presentation from three mono (each) sound sources in our home theater electronics chain, but  not as many reflections as we need with a two channel system.

With a room that is 25′ w x 12′ h x 50′ l,  with 8″ poured concrete walls and 18″ of top soil for a roof, what more could we ask for? Someone pinch me please. More in part II.

 

 

 

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Filed Under: Environmental Building, Room Acoustics, Uncategorized Tagged With:

The Differences Between Sound Proofing Materials Explained

April 26, 2012 by Leave a Comment

Soundproofing Materials

Soundproofing materials use and proper selection are determined by how much noise level we are dealing with and where that noise level originates from. If the unwanted noise is originating from the outside of the room or structure we seek to soundproof, we need to use barrier soundproofing technology. We need to place a barrier between us and the noise we are trying to get away from. If our noise levels originate from within our room we are trying to soundproof, we will have to use absorption technology. On some occasions, we may have to use both barrier and sound absorption technology together to absorb excess energy within our room and to keep that energy from leaking into adjacent structures.

Building a Barrier

Barrier technology is just what the name implies. We construct a barrier between our room and the noise source. If we live on a busy street and the traffic interferes with our recording studio, we need to build a barrier between us and the car traffic. If we live in an apartment and we have a noisy neighbor, we need to build a barrier between our neighbor and our apartment. Barrier technology is not cheap to do and requires special construction techniques. One must choose what materials to use and how many. One must also decide what construction method we will use in assembling our barrier. Once we build our barrier, we then must install it within an existing structure. Care must be taken to mechanically decouple our new barrier wall or structure from the existing room. We must use vibrational control assembly and installation techniques.

Absorption Technology

Absorption technology is a different animal. Absorption technology really has nothing to do with mass except at low frequency absorption issues. Absorption technologies are usually light weight and easily positioned. The process of absorption is a physical one where sound energy is converted to heat. Once this conversion process has taken place, the sound energy is lost forever. It can not be changed back to sound once it has been changed to heat. There are numerous sound absorbing technologies available in the marketplace.

Barrier Materials

Barrier technologies are built with standard construction materials. Some materials used in barrier technologies include plywood, multiple density fiberboard, drywall, and even concrete and lead. Barrier technology materials are heavy and have high densities to minimize vibration. Vibration control becomes the design goal of a barrier. Air born sound energy strikes the barrier and is then converted to mechanical energy. This mechanical energy travels through the barrier we just constructed and these vibrations must be reduced in a systematic way to insure that they are reduced when they enter our room. It is difficult and very expensive to stop all noise issues. The best we can try and achieve is to lower the outside generated noise levels below a minimum acceptable level.

Must Reduce Vibrations

To minimize vibrational levels, we must construct our barrier in a vibrational reducing manner. The correct term for this construction methodology is termed constrained layer mass damping. We use different layers of materials that are constrained or combined together to achieve a mass that then serves as a vibrational damping unit. Each layer of our several material barrier must be assembled in a way that reduces vibrations. For example, if we are using plywood and drywall as two of our barrier materials, we must join these two materials together with another layer of material. In barrier technology creation the more materials used usually is for the better. We can join our plywood and drywall together using an acoustic glue that will provide the necessary adhesion benefits to keep the two materials together but not so together that the assembled unit acts as a single piece of material. Remember, our goal is to reduce vibrations by forcing them to go through different materials all with different densities. This process correctly done, can significantly reduce vibrations.
Absorption Materials

Absorption technologies can be common acoustical foams, draperies, numerous fabrics, and even furniture. Our acoustical goal with absorption technology is to provide enough of the chosen material, so that we can cover all the necessary surfaces of our room we wish to soundproof. A combination of sound absorbing materials usually works best. In most rooms where soundproofing within our room is the goal, we must cover all wall surfaces with sound absorption technologies and even add additional materials throughout the room to absorb lower frequencies than standard acoustic wall treatments can handle. A large stuffed chair can be used to absorb lower frequencies that our acoustical foam panels can not. If we want to scientifically attack our absorption issues and deal with them scientifically, we can use low frequency absorbers that are specifically designed to handle the low frequency energy issues specific to our individual room.

Sound proofing materials are problem specific. If we need to stop unwanted noise from outside our rooms, we need to build a barrier between ourselves and the noise source. We need to use materials that have high mass and densities. Barrier materials include plywood, drywall, concrete and even lead. Barrier materials have mass and density. If we need to absorb unwanted energy from within our room, we use absorption technologies. Absorption technologies include acoustical foams, draperies, and even a large chair.

Filed Under: Environmental Building, Room Acoustics, Uncategorized Tagged With:

How To Sound Proof A Door

April 24, 2012 by Leave a Comment

A door like a window can be a portal for noise or unwanted sound to enter our room. Acoustic doors have to perform a dual function. They must provide a barrier between the inside of the room and the outside noise levels. They also must keep sound energy generated from within the room from leaving the room and entering other adjacent rooms. They must do this on a temporary basis because they must open and close to allow for individual access into and out of the room. As they open and close continually, they must seal correctly, so that no gap exists between the door edges and especially the door bottom.

There Is s No Substitute For Mass

Our door through its use of barrier technology must have mass. Multiple layers of materials arranged in vibration reducing manners is the goal. Multiple density fiberboard (MDF) is a good material that provides us with the mass we need to begin our door construction. Remember from past discussions, that not only do we need mass in our material selection but we need to have different materials with different densities, so we can slow down vibrations coming through our door. Vibrations will lose energy if they have to struggle through different material types with different densities. If we use MDF, we can mate it with a plywood. Plywood has numerous layers that are fitted together into a single piece of material. Now we have two different materials that provide us with the appropriate densities.

Proper Assembly Required

We need to take our MDF and plywood and then assemble these two materials in a manner that reduces vibrations. Sound produces and is produced by vibrations. When electromechanical sound from our loudspeakers is produced and strikes our door surface, it is turned into vibrational energy. This mechanical vibrational energy sets the surface it strikes into motion. When it strikes our door, our door must be made in a manner that allows for this to occur, but reduces the vibrations through the way it is assembled. To reduce these vibrations, we use a process termed constrained layer mass damping to sandwich our chosen materials together.

Constrained Layer Mass Damping

Constrained layer mass damping is a process where we take different material types with different densities and arrange them in a manner that keeps vibration reduction in mind. We sandwich each material together with another material such as an acoustical glue. The more materials the vibration has to go through, the better for its reduction. With our MDF, plywood, and now glue, we have three materials that vibrations must go through. The more the better to a point.

MDF / Plywood

If we place MDF as the outside of our door surface, we then can add our plywood underneath the MDF. To secure the two materials together, we need to glue them together. We use an acoustic glue that will keep both materials together and provide another material type with a different density that our unwanted vibrations must go through. If we use MDF on the other side of the plywood we should use a MDF piece that is a thicker or not as thick piece as the front piece. Remember, we want to vary the density or mass of the piece and the thickness of the material to further “confuse” the vibration. We should have as our acoustic goal to have our finished door weigh at least 9/lbs./sq.ft. to provide the necessary noise stopping power.

How to Hinge

Once we have our door assembled with its associated weight, we will need to place it into the door frame. If it is an existing door frame, we must make sure it can support our new acoustic door’s weight and then seal correctly around all door edge surfaces. We may want to consider building a new door frame to support our new door. If we do not and choose to keep our existing frame, we must be sure it is sealed to the existing room structure with a healthy application of acoustic sealant.

To support our new heavy acoustic door, we will need hinges. A cam lift hinge will work well in this scenario. A cam lift hinge will assist us in proper sealing due to its construction method. A cam lift hinge can also support the weight of our new acoustic door. Numerous finishes are available on cam lift hinges to accommodate any decor.

Seal All Gaps

Finally, we must seal our new door to the door frame. All door edges must close squarely and seal properly. Special attention must be paid to the bottom of the door. This is an area where their is a lot of wear and tear and providing a continual seal every time is a must. We can use a brush type sealing strip that collapses when the door is opened or closed but then springs back into place to provide a good seal. There are numerous sealing strips available. Care must be taken to choose the correct stripping that matches the use of the door and the acoustical objective.

A door and window can be the weakest link in our room. We must use mass in our door to stop vibrations. We must assemble the materials in a manner that reduces vibrations and we must sure it seals correctly every time it opens and closes. It must be the correct mass and stiffness and be able to achieve a sound transmission class rating of at least 55.

Filed Under: Environmental Building, Room Acoustics, Uncategorized

How To Sound Proof Your Ceiling

April 22, 2012 by Leave a Comment

Sound proofing our ceilings is probably the most difficult part of our room to deal with, simply because we have to support any material type we decide to use with our existing ceiling or by building a new structure. If we are dealing with a lot of noise from adjacent rooms, we will need to measure how large of a noise problem we actually have, so we can figure out exactly how much material we need to use. We definitely don’t want to use any more material than the noise issue demands since we have to support any material we will use with the existing structure or build a new one.

Measure The Problem

Our first task is to measure how much noise we have to deal with. If our noise is coming from our own room and we need to seal that noise from drifting into other rooms, we need to measure the noise from within our room and start with that issue first. If the noise is external to our room, we need to measure it and find how much of a noise issue we have to deal with. Remember from past discussions, that both noise sources whether external or internal require different forms of acoustic treatment. Barrier technology is used to keep noise from entering our room from external sources and also keeping our own noise levels generated in the room from “bleeding” into existing structures. If we need to control room boundary reflections and general small noise levels within our rooms, we can use absorption technology.

If our noise levels are determined to generate from external causes we will need to use barrier technologies to place a barrier between us and the noise. Once we have determined how much noise we have to isolate ourselves from and at what levels we are dealing with, we can choose the appropriate barrier materials and technology we need. All barrier materials have mass and weight associated with them. Barrier technology is all about controlling vibrations from sound pressure waves that are produced by our noise source. Mass and high density materials have to be arranged in a certain vibrational controlling method termed constrained layer mass damping. Multiple layers of materials with different densities are arranged in a manner that produces the least vibrational transfer of energy.

Build a Noise Barrier

To build a barrier for our ceiling, we will start with two commonly found construction materials. We can use plywood and drywall or gypsum board. We can start by taking our plywood piece with a 1/2″ thickness and then placing an “acoustical glue” between the plywood and the 3/8″ layer of drywall. Acoustic glue never hardens completely and the two materials that it is bonding with “float” against each other. This layering of materials technique is termed constrained layer mass damping.

In a constrained layer, mass damping configuration, all layers of high density materials must be separated or mechanically decoupled from each other to minimize vibrations from transferring from one piece of material to another. By isolating each higher density piece of material with a lower density or viseoelastic damping compound, the vibration must travel through all of these materials and as it does it losses energy and this is our goal. If we can reduce the vibrations strength, then we can minimize the sound or noise energy that vibrations can produce.

To further increase our barrier’s strength against vibrations, we can physically arrange the materials in ways that will reduce vibrations. If we are using multiple layers of plywood, we can arrange one piece of plywood one grain direction and position the other in a cross grain direction from our original piece. This running of the grains in different directions can go a long way to assist us in reducing our vibrational levels.

Installation Is Critical

Installing our new barrier technology requires care and careful consideration. We must install our new ceiling in a manner that continues our vibrational isolation theme. We must separate the new ceiling from the old or existing one using vibration isolation techniques. We first install a series of isolation tracks that our new ceiling will attach to. These tracks will physically decouple our new ceiling from the existing one and create an air space between the old and new ceiling. Air is also a vibration reducing material and can be effective as another layer for vibrations to have to work themselves through.

Watch Those Edges

We must pay particular attention to the edges of our new ceiling. In most ceilings, the ceiling edge surfaces touch the existing walls. There is no gap or space between the edge of the ceiling and the wall surfaces. While this looks nice in normal environments, it can be detrimental when dealing with vibrations that contribute to noise. Our new ceiling or barrier must have itself physically isolated from our existing room structure by leaving a gap between our new ceiling and existing wall structure. This physical gap serves two purposes. First, it isolates our new ceiling from the walls which will prevent the vibrations from our walls from entering our new ceiling barrier. Secondly, the small gap will prevent vibrations from our ceiling from entering into the walls and causing more issues. This small gap will be filled in with an acoustical sealant.

Absorption Inside Our Rooms

Noise levels in our room can be controlled through the use of absorption. We can absorb excess low, middle, and high frequency energy inside our rooms using many different types and forms of absorption technology. If we have noisy office equipment, we can place these units in sound isolating cabinets. HVAC noise can be controlled by lining our duct work with special foam technology that can reduce the air flow in the duct work itself. We can also reduce the fan noise by lowering the fan speed to reduce air flow. We need to lower the air flow down below 340 feet per minute.

Sound proofing your ceiling is not an easy task. If we have to build a barrier between our existing ceiling surfaces and outside noise levels, we really need a professional to design and install it. One can spend more money and energy making mistakes by guessing how much material to use and building and installing it incorrectly, than it would take to actually have a professional do it. Controlling noise levels within our room using absorption technologies can be a do it yourself project with adequate research done ahead of material selection and installation. `

Filed Under: Environmental Building, Room Acoustics, Uncategorized

Sound Proofing Windows – The Weakest Link

April 20, 2012 by Leave a Comment

Windows in our home theaters, personal listening rooms, and professional recording studios are the weakest link in the whole acoustic soundproofing process. In order to examine how much of an issue they create in the total sound proofing process, we need to examine how weak they are in stopping outside noise from entering the environment we choose to soundproof. To show this weakness, we look at a number called a sound transmission class rating or STC.

Sound Transmission Class Rating

A sound transmission class rating is a number that tells us how much noise is held back or prohibited from transmitting through the particular structure. The STC scale is a special type of scale similar to the Richter Scale used to measure earthquakes. A existing sound transmission class rating of 28 is not satisfactory and is the STC rating for most single pane windows. If we increase the STC rating to 38 we have reduced the noise level by 90%. If we have an existing window that has an STC rating of 28 and we increase the STC rating to 43, we have reduced the noise levels by 95%. An increase from 90% to 95% means that 60% of the remaining noise has been reduced. There is also a difference between the measured STC rating and human perception. Typically, a 95% instrument measured STC, means that a human will perceive a 75% noise reduction. Small increases in the sound transmission class rating create a lot of noise reduction.

Current Misconceptions

It is common to hear people say that single pane windows do not do much for outside/inside or inside/outside sound reduction. This is a true statement. This comment is usually followed by stating that a double or even a triple pane window will work much better. Lets examine the STC ratings for both of these scenarios. A single pane glass window has a STC rating of 26 – 28. A dual pane window has a STC rating of 26 – 33. The average STC rating then becomes 27 for a single pane and 28 for a dual pane window. Our acoustic goal is to have at least a 75% reduction in noise levels and neither a single or double pane window meets this requirement. Neither a single or double pane window accomplishes this goal.

Build A Dam

What is the solution? Do we replace our windows with walls? Do we add more glass or thicker glass? The answer goes back to using multiple layers of materials to stop vibrations from moving through the window and into our rooms. Remember from past discussions, that we are dealing with sound energy and its associated vibrations. We need to stop these vibrations by creating individual vibration “dams” if you will, that hold back parts of the vibration in one layer of material and then as that remaining vibration transmits to the next material layer, it is reduced even further. We need to put a series of “dams” between us and the vibration.

Use Multiple Layers

Thicker glass is an option, but it is not just thickness we are concerned with. It is the nature or the thickness and how the thicker glass is used in combination with other layers of materials. One option is to use laminated glass. Laminated glass is two pieces of glass sandwiched together with an inner layer of plastic between each layer. This three layer system follows our example of using multiple layers of materials to stop vibrations. The vibration hits the first layer of glass and is reduced by an amount. The vibration then goes through the layer of plastic and is reduced further. Finally, the vibration hits the second layer of glass and is reduced even further. This series of constrained layers of mass damped materials produces a better barrier to stop noise. A good glass thickness for each layer of glass is 1/4″. Greater thicknesses can be used but 1/4″ is a good starting thickness depending on existing noise levels.

Leave Existing Window In Place

We can leave our existing window in place and use it as another layer or “dam” in our vibration reducing link. We can add our new laminated glass in front of the existing single or double pane window. Air is also a material that we can use to our benefit. We can place an air space between the existing window and our new laminated window. For best results, the air space should be at least 5″. We can even repeat the process and add the same laminated window to the other side of our existing window, leaving the 5″ of air space between the existing window and our new laminated window. Now, we have a laminated window on both sides with a 5″ air space on each side of our existing window.

No Leaks In Our Dam

We must also make sure the window is sealed correctly with the existing structure. Using our example of a dam to hold back noise, we must not have a leak or hole in our “dam”. Even the smallest hole will let in noise and negate all the work we have gone through building our laminated window. We must make sure the window is sealed within the existing frame and that no air leaks are present. Another detail we can attend to making sure the window does not vibrate under any circumstances. Remember, vibration produces noise and that is not our goal. We can use a spring loaded seal to accomplish this.

Windows let the most noise through into our rooms. We do not need to replace our existing windows, we can simply add different materials to our existing windows and create a series of layers of materials with different densities to minimize noise transmission. Additional glass sections can be added with an air space between or we can opt for thicker laminated glass. Whatever the direction, all construction tasks must be taken seriously from beginning to end.

Filed Under: Environmental Building, Uncategorized

How To Sound Proof An Office On A Budget Part – III

April 8, 2012 by Leave a Comment

In Part I and II of How to Sound Proof Your Office, we discussed how first and foremost, we must quantify what our actual noise issues are. We must put a number to the noise. Next, we need to find out if the noise is being generated from outside the office or from inside the office. Depending on the noise source and position, we will use different technologies to minimize the noise issues. We minimize so noise levels do not rise above acceptable levels within an office environment. In most situations reducing pressure levels that allow for normal speech and work related endeavors to move along uninhibited is the acoustic goal. Eliminating noise completely is usually not an option. If our noise is generated from outside our office room, we discussed barrier technologies and their application. If the unwanted noise is coming from within our office room, we must use absorption technology.

Speech Intelligibility

Reflections from our office wall surfaces confuse our brain’s ability to localize sound sources. Reflections also mix and blend with the vocals blurring and smearing our voices inside our office room. Their is a term for this phenomenon. It is called speech intelligibility. We must have reflections in our office minimized and our reverberation times in the office room below certain levels in order to hear speech clearly and “intelligibility”. There are a series of numbers that one needs to look at, but a discussion of them is not necessary. These numbers are easily achieved using absorption technologies.

How Much Noise?

The most important thing we need to consider is how much energy will be generated from within the room. Once we know that, we can definitely choose the correct rate and level of absorption we need to use. Normal office pressure levels from 65 dB to 70 dB can be maintained with using numerous commercially available and affordable products. If you have a dropped ceiling, you can use acoustic ceiling tile that is made to fit in those ceiling types. One can also add absorbing material to the backside of the ceiling tile, for added absorption values. There are numerous wall treatment options for controlling wall surface reflections. Most are some type of fiberboard filled or unfilled with a fabric covering stretched over the face.

Door Must Be Sealed

The door in our office must be sealed, so that when it closes, there is no air leak between all the door surfaces and the door. Even a small opening can allow a large amount of unwanted sound energy to “bleed” into the office. Think about it as a hole in a dam. All the water pressure built up on the other side of the dam or door is forced into that small opening and then into the office room itself. A strong commercial grade weather striping can be an affective seal. Brush type strips are also used that have a series of bristles on them, so that the door pushes them in one direction which adds a sealing action to the joint or opening.

Windows

Windows in our office are the weakest link in the acoustical chain. Windows create harsh surface reflections and allow for sound energy from the outside to come in. Double pane windows with a vacuum seal between each pane is a good start. Triple pane windows are better. This is no place to try and save money on. Windows are expensive and are very important. Make sure your budget allows for some type of window covering, so that one can cover the glass to reduce sunlight and stop unwanted window reflections from entering our office environment.

Office Equipment

Office equipment noise is another issue. One piece of electronic equipment in our office does not generate or add much background noise to the total amount in the room. However, once we have 6 or 7 pieces of equipment in the room, both noise and heat levels can rise. Separating the equipment from each other and moving the equipment to different parts of the room is an option. However, in most office scenarios, this is not possible. Keeping the equipment all together facilitates use and ease of operation. Placing the equipment in sound isolating cabinets is a good option. The professional recording market will have these types of cabinets, since they deal with equipment noise on a regular basis. These cabinets will also have venting for heat and air movement.

If the excess sound energy is coming from inside our office rooms, we must use absorption technologies to reduce the noise levels, so that the work environment is quiet enough for all parties concerned. We can use acoustic tiles for our ceiling and even improve upon their performance by adding absorbing foam to their backside. We can use fabric covered panels for the wall surfaces. We just need to make sure that they are absorbing at the proper rates and levels for speech intelligibility. Windows are our weakest acoustical link and must be treated so. Office equipment noise can be reduced through the use of sound isolation cabinets.

Filed Under: Environmental Building, Uncategorized

How to Sound Proof An Office On A Budget Part-II

April 6, 2012 by Leave a Comment

In Part I of How To Sound Proof An Office On A Budget, we focused on determining what our real noise issues are. Is the noise inside our room coming from outside our room or is it coming from inside our office. What is its rate and what is its levels during our work day. How far above the norm are the levels. We discussed how to obtain two numbers that we could use in the selection of certain material types with certain densities for minimizing our noise issues.

Outside Noise

If the sound pressure or noise is coming from outside our office, then we need to place a barrier of some sort between ourselves and the noise source. This barrier or wall will have to have a certain mass or density depending on how much noise is generated from outside sources and interferes with the noise levels in our office room. Lets say we have 10 dB more sound pressure generated from outside our office than we want. We need to put up a barrier. That barrier will have a number attached to it. The number once the barrier is assembled is called a STC or sound transmission class rating. The number determines how much sound energy the structure inhibits or losses. The higher the number, the better, but we do not need to have a high STC number in our barrier or wall. We need to have the wall number be at the level we need to stop 10 dB of sound pressure. This will require a STC rating of at least a 45.

So Many Choices

There are numerous material types we can use to build our barrier. We can use drywall or U.S Gypsum board. It is inexpensive, well relatively so, when compared to other material types. It is also available in different thicknesses. Multiple density fiberboard or MDF is also available in numerous thicknesses and has a higher density than drywall. It is also easier to work with because it will not cover you with drywall dust during installation and outside finishing. Plywood is another type of material that is available in numerous thicknesses. It also has a good surface for finishing. It also has the highest cost when compared to MDF and drywall.

CLMD What’s This?

To achieve our barrier STC of 45, we need to use a fancy process called constrained layer, mass damping,(a bunch of different materials glued together) used in the construction of our barrier or wall. Lets use MDF. We need to have different thicknesses of MDF, so that we can sandwich them together in a way that reduces vibrations. We know that sound or noise outside our office is produced by vibrations and those vibrations enter our office air space as air born vibrations. To stop those vibrations, we need to build our barrier or wall in a manner that reduces vibrations that strike our wall’s surfaces. If we take a 1/2″ piece of MDF and attach it to a piece of 3/4″ plywood, we have assembled a “sandwich” that is made of two different materials each with different densities. If we “glue” these two pieces together with an acoustical sealant of another common commercially available product such as Green Glue, we have created a barrier composed of different layers of materials that are constrained, thus mass damping occurs.

How To Install

We now have to isolate our new barrier wall from our existing wall structure. This process will add another layer of material (air) between our new wall and existing wall. We will attach a isolation rail to our existing wall and then attach our new wall to the isolation strip. We must not touch any side wall, top or bottom wall, with our newly created constrained layer, mass damped, wall. We will recess all new wall edges from the existing wall by 1/4″. This 1/4″ trough will be filled with acoustic sealant. Once again, as with our vibration reducing wall structure, we are isolating two surfaces, the new wall from the old wall, using an acoustical sealant. We were separating each wall surface from each other with another material, so that the vibrations have to travel through numerous material thicknesses which slows them down at predictable rates and levels.

Reducing outside noise levels in our offices, requires that we first determine what our actual noise levels are that are disruptive inside our office room and then build a barrier between our office and the noise source. We need to build our barrier in a special way that minimizes vibrations using special construction techniques. We then need to install our new wall using another vibrational isolating technique which minimizes vibrations also. Part III, will focus on How To Sound Proof Our Office using sound absorption.

Filed Under: Environmental Building, Uncategorized Tagged With:

How To Soundproof An Office On A Budget Part – I

April 4, 2012 by Leave a Comment

In an office, we have noise that takes many forms. We have the most obvious, which is speech. However, there are numerous other noise producing sources that must be considered. We have machine noise from office equipment and telephones. We also have the noise of air rushing through the HVAC system. We could have projector noise to deal with in the conference room. Can we hear the cars outside our office? All of those systems can produce large levels of ambient noise which is then the benchmark that vocals have to compete with. The only way to compete with this background noise is to increase the gain on the speech in the room or as my associate always says on the telephone, “please speak louder”. Lets approach this one noise level at a time.

We Must Have Numbers

First, and probably the most time consuming step is to figure out what are noise problem actually is. This is critical in all noise evaluation scenarios nor matter what the budget restriction are. If we can quantify the actual noise level that we are dealing with, we can choose the correct amount and type of materials that we need which will avoid trying certain materials by using just guesswork. We can accomplish this by measuring the sound pressure levels throughout the day in our office.

Tools Needed

For illustration purposes, lets view our problem as an energy pressure issue. Lets go to Radio Shack and purchase a SPL meter. Take the meter, place it on the a-weighted scale, and set it on your desk. Adjust the dB dial to 60 and start from that point. Watch the meter as the day goes by and look for two types of numbers to use in our calculations. First, look at the average sound pressure level that is generated during the day when your door is closed and it is just you and your office. Make a note of this number. Make a note of the number when you are talking on the telephone. Do this throughout the day.

Measure This

If the office next door is showing a video presentation and there is audio attached, measure those pressure levels. If the office down the hall is throwing a birthday party, measure how much energy is in your office when the party is going on. Measure the levels when the air conditioning is off and measure the levels when it comes on especially the ones that have large internal fans. Measure the levels when you have one person in it. Measure the levels when you have two or more people in your office at your next meeting.

What Do All These Numbers Mean

Once we have the sound pressure level in your office measurement that shows the quietest moments and then we have the measurement that shows the moments with the most noise, we can look at the lower figure as our “noise floor”. This is the number that we will subtract from the high number to determine what we are dealing with and this number will show us how much sound pressure we need to absorb with our soundproofing materials. This number will tell us what type of material to use and what its density requirements are. Mass cost money and we only want to use what we need to use, no more, no less, to solve the room’s noise issues.

What Do These Numbers Mean?

Normal speech in an office environment is around 65 – 75 dB. If we look at our numbers that we have gathered and look at the number when we had one person in our office speaking, that number should be around 70 dB. That is a typical number for all ambient or background noise coupled with speech. If we have a number of 75 – 80 dB when we have just one other person in the room having a normal business conversation, we probably need to focus on blocking some sound energy from getting into our room.

Sound or noise issues that come from outside our rooms and then enters our room must be dealt with using barrier technology or in simpler terms mass. As we said before, mass costs money and we need to know how much mass we need to solve how large of a noise issue we really have. If our lower number in our office through the day is 65 dB and then raise quickly such as when there is a video/audio presentation in the next room, we know this is a one time or in frequent occurrence that does not warrant using a permanent full time solution for.

In Part-II, we will examine how we take our numbers we have gathered and translate those numbers to an acoustical material list that will deal directly with the numbers. No guessing on how much and how thick. The only decision will be what color.

Filed Under: Environmental Building, Uncategorized
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