This blog has been updated from its original post to reflect new information regarding building a recording studio in a basement, updated on 11/11/19. Start With Room Size People regularly ask me whether or not building a recording studio in a basement is a good idea? If the room itself is a good size, would […]
Today we’re going to talk about how to soundproof an office. A lot of people work in offices, they’re noisy places and sometimes you need that peace and quiet to get on with your work. In an office, you have a lot of different sources of sound energy. We have telephones male female voice, demonstrations, […]
Welcome to the third Acoustic Treatment Google Hangout with Dennis Foley from Acoustic Fields. The below broadcast went live at 11am on Tuesday, July 15th, so thank you for your questions on the room acoustic issues which have been troubling you. Here are the questions we covered this week: 1. Do you know much about […]
This video is from the Treehouse Masters show. On this episode, the builders explore a small recording studio built in a treehouse. This treehouse studio was built for Bear Creek Studios. The studio has a compost toilet and a sink in the bathroom, electricity throughout the place, and has cork soundproofing. While the actual work […]
Soundproofing does not exist. Nothing really can be made completely sound proof as the name implies. You can not keep all the sound energy at all times, in or out of your room. All you can do is manage the sound energy that originates from outside your room, with certain barrier technologies. Sound energy that originates within our room must be managed using sound absorbing technologies. It is the management of this energy that we must focus upon and the processes involved, not “proofing” anything from sound.
What the name soundproofing really implies is noise management. How much noise do we have to keep out of our rooms and how much energy do we have to keep within our rooms. What frequencies does that noise reside at. What is the amount or amplitude of the noise we wish to manage or keep out or inside of our rooms at these particular frequencies. We must quantify the noise to determine the composition of our barrier. Soundproofing is all about using barriers that are specifically designed to handle the “noise” frequencies between the sound source and the receiver.
Barriers differ from each other depending on the frequencies we are trying to keep out of our room. Frequencies below 125 Hz. require different barriers than frequencies above 125 Hz. The material used in the barrier is critical, but it is the density and arrangement of materials that we must concern ourselves with. With barrier technology, we are reducing vibrational energy that is caused by sound pressure waves and rays exerted upon the barrier surfaces. Arranging different materials with different densities in a manner that reduces vibrational energy is the art and science of constructing the proper barrier for the measured noise issues you are faced with.
When we live on a noisy street, we must use barrier technology to construct a shield between us and the noise source. This barrier must use vibrational science to minimize the transmission of sound energy from one side of the barrier to the other. If its the bell on some child’s bike that is a concern, then the garbage truck is another issue entirely. Frequencies below 125 Hz. are difficult and the barrier technology required is expensive and can be space consuming because of its required mass and densities. Frequencies above 125 Hz. are much easier to manage.
How Thick ?
To find out what barrier technology we should use, we must first determine how much of what frequency, we need to isolate ourselves from. The child’s bell is of a different frequency range than the garbage truck muffler. It is also of a much larger magnitude in strength. The child’s bike bell can be isolated from completely. All we can hope for with the garbage truck, low frequency, energy is to reduce its impact in our rooms, so that it is below that of the room’s use acceptable noise level. Stopping low frequency noise completely is not an option. We must lower its sonic impact and bring it down below the intended use of the room, so it does not interfere with our sonic objectives of our room.
Sound Transmission Class
STC or sound transmission class rating is an antiquated measure of noise levels and rates from 125 Hz. – 4,000 Hz. It does not measure below 125 Hz., so for any noise that involves frequencies below 125 Hz.,we must look to other units of measure. There is software available that will construct suitable barriers to deal with the energy below 125 Hz. Barriers that impact energy below 125 Hz. are best left to professionals. There is plenty of information for barriers above 125 Hz., but vibrational isolating construction techniques must be followed even with these frequencies.
Barriers are constructed to minimize vibrations. Sound energy from an outside free field source radiates its energy in the forms of waves and rays and this energy travels towards us. It strikes the surface of the barrier we have constructed. To build the appropriate barrier we must use multiple layers of different materials that have different densities. The composition structure of the material and the material’s density, all are considered when we create the barrier.
Our vibrational goal is to force the wave or ray to have to travel through different “fields” of materials. These materials are arranged in such a manner that based on the vibration’s frequency, they slow the vibration as it travels through our barrier from its originating end, through the barrier, and eventually into our room. Our goal is to reduce the magnitude or strength of the vibration itself by making it travel through a vibrational reducing, “obstacle course”.
Maybe we use materials that have densities that are larger for the outside surface of our barrier and work through the barrier construction with materials that have lesser densities. Maybe we start with materials that have lower densities and work through the barrier with materials of larger measured densities. It all depends on what frequency range and how much of each frequency we need to isolate against. Our goal is to reduce the structural vibration’s amplitude so it has less audibility when it converts to an acoustic wavelength.
The use of the term “soundproofing” should be changed to noise management. Clients often use the term without knowing the context into which the term is placed. Their expectations are larger than our current science and in most cases much larger than their budgets. Can we “sound proof” for frequencies above 125 Hz.? Of course, as long as our barrier constructions takes into account the magnitude of the energy we must isolate from. Can we “sound proof” for frequencies below 125 Hz.? The answer depends on which frequencies and how much of them we have to deal with. If we look at frequencies from 125 Hz. down to say 80 Hz., we have a fighting chance, once again, depending on energy strength. Frequencies below 80 Hz. are are a different issue and the term soundproofing and even noise management becomes lacks certain meaning and applicability.
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Methods And Materials
In part one, we examined vibrations and the different mediums that these vibrations travel through. In part two, we examine how these vibrations produce sound in our structures by traveling through them. The way things are built and the materials used are critical in minimizing vibration transmission and incurring the appropriate sound transmission loss for our structures.
Staggered Construction Techniques
Keeping all of this in mind, a wall that is deemed “soundproof” should be two walls independently separated by air. Each sill of the two walls must be distinctive and the studs in each wall must be staggered, so that they do not line up so sound energy will see a “road” to take. Each sill must be attached to a very solid surface. This is usually concrete which is very dense and makes for a good attachment point. The sill should be isolated from the concrete further by using a damping compound. There also can be no “leaks” for acoustic energy to travel through. Acoustic or sound energy is like water, it will run to the area of its least travel resistance.
Vibrations Cause Resonances
Vibrations cause resonances. One quickly realizes the power of resonances when they deal with room modes between two parallel surfaces within their home theater, listening rooms, or professional recording studios. We have discussed how resonances can be reduced if we use mineral wool or some other type of fibrous materials. However, resonance can also be our worst enemy. Every material we use has a frequency of resonance. The exact resonant frequency will be dependent on the mass and physical dimensions. When sound energy strikes the panel and it is at the panel’s frequency of resonance, the panel will be set in motion and will start moving like a diaphragm. This minute movement will will assist in energy transmission through the structure and may even create its own sound. All multiples of the panel or wall’s resonant frequency will also be affected.
Manage Not Eliminate
We can not eliminate vibrational transmission through our structures, but we can minimize it and reduce its amplitude down to an insignificant level. To accomplish this, we use damping. Fibrous materials or damping compounds can be useful. Damping aids our vibrational transmission chain by reducing the vibrational levels of the materials it is applied to. One could say that damping prevents materials from continuing to vibrate once they have started. If we use multiple materials that are damped, we must select materials, so they do not have the same frequency of resonance. In past studio builds, lead was used extensively because it had a high mass density and it was limp so that its resonant frequency was below audibility. Now, due to health regulations, limp mass vinyl is more common although not as dense as lead.
Floors Are Always Moving,/strong>
Our floors are another room boundary surface area that must be dealt with when we are examining soundproofing. Noise sources that cause us sound energy issues are almost all connected to the floors of our home theater, listening, and professional recording studios. Footsteps are a good example of contact with the floor and most of the time our speakers sit on the floor. How about that sub woofer in our home theaters. If we want to keep the sound energy in our personal listening room from reaching the rest of the house, we should use the basement with its dense concrete floor. For a project studio, we should go to the top floor, so no one is above you.
Floors Retain Energy
Our floors contain a great deal of energy. The moment sound energy enters the floor, it will move and travel through the whole floor. Even though it is a layered structure, all layers have to be attached at some points. It is through these points of contact that energy transmission can occur. From a design standpoint and taking all of this into consideration, it is best never to let the vibrational energy into the floor at all. Carpet is a good start for footsteps. A foot stepping on a carpet will produce hardly any sound through vibration. In multiple floor apartments, carpeting is always recommended in construction drawings for this reason.
Speakers On Our Floors
Speakers provide for a completely different set of issues. Our acoustical goals with our floor standing, energy producing, speakers must be to reduce and minimize the energy produced from low frequencies by our speakers. Rugs will not be effective for our low frequencies because they are soft and low in mass, so they will allow transmission of energy especially low frequencies. One should use spikes in your speakers because the difference in abrupt change of mass at the floor and spike contact point. This small contact area will not let many vibrations through it. Spikes are not funnels for energy into the floor and out of the speaker cabinet as some spike and cone designers will tell you. Why would we want to dump all that energy into the floor and get it moving.
Floating floors are a popular vibrational reducing technology. They do not really float without any point of connectivity, but their connection points are distributed throughout the floor structure surface area. A floating floor is really a completely separate structure that is isolated with neoprene supports. It is best that the sub-flooring under our floating floor be as dense as time and money will permit.
Windows And Doors
Windows and doors within our room are other portals through which sound can enter. We have all heard that an open window is a perfect absorber. It is perfect because once sound leaves through the window it never returns. On the other side, sound can enter through our closed window and the surrounding structure. Doors must be constructed of multiple layers of materials that have high sound transmission ratings. Better yet, take our multiple layered door and build two doors and separate them with a layer of air. This structure is termed a sound lock and works just like an air lock on a spaceship.
Room Planning For Vibrations
What is important in planning a room is understanding how sound is transmitted through a structure, and becoming familiar with a few of the common techniques for limiting its transmission. It is the contact points between structures in our barrier technologies that are pathways for sound transmission. To reduce vibrational pathways takes planning and calculations which are best left to a professional. One contact point between expensive structures that is not properly designed and installed can negate the performance of the whole wall.
Sound And Vibration
All sound is created by vibrations. Sound vibrations must have a medium to travel in. The most popular and familiar medium is air and we hear those sound vibrations everyday through air. Air does a reasonable job of transmitting sound vibrations because it has low mass and can transmit sound energy over a wide band of frequencies.
Air is a good medium for low frequencies but less effective at higher frequencies. When you are farther away from a loudspeaker, you will notice that the high frequencies are less pronounced or in audio jargon, rolled off. If you go to a live performance and you do not like piercing highs coming at you at large pressure levels, sit farther back. If you are trying to get the attention of your friends to help direct them to your seating area and you call out their names from far away, the same muffled high frequency effect occurs.
Your room whether it is a listening room, home theater room, or professional recording studio will have objects within it that have much more mass than air does. This increased mass of these objects will be less effective at transmitting shorter wavelengths namely high frequency energy. When you hear the stereo or band playing in the next room or adjoining structure, one usually “hears” the lower frequencies because they are transmitted through the structure more easily than higher frequencies. With these examples in mind, lets formulate a few guidelines:
1. Soundproofing is really about lower frequencies.
2. All sound that is transmitted needs a medium to move through and that medium must be continuous.
3. In our audio rooms the medium will be a solid structure with mass such as drywall, wood, or concrete.
Lets look at a sound wave as it leaves our neighbor’s stereo system. When the frequencies strike our wall surface, some of the energy is reflected back to the source and some of the energy goes through the wall itself. This is the point where people usually get confused about sound treatment and sound proofing. If we are trying to keep the sound energy within the room, then the room’s reverberation times will increase and we need to use acoustical treatment within the room. The sound energy that escapes our room, will not add to our room’s reverberation signature, but will annoy all individuals in adjacent structures. This is where soundproofing comes in.
The hard surface of our walls is a partial explanation for this phenomenon. It is the hardness of the wall’s surface, but the composition of the wall itself. The wall has increased mass over air and this increased mass is like your car hitting a brick wall abruptly. The air is what we term to be compliant and the wall is much less compliant. This wide level of density changes from air to a solid wall changes the transfer of energy ratio. Thus, only a fraction of the energy that was in the air to start with will penetrate the wall itself. This is why our homes are quieter when all the doors and windows are closed.
Energy Not Lost
The energy that does not penetrate our walls must also be looked at and examined. We know from the laws of physics that the energy can not simply vanish. This comes from the First Law of Thermodynamics which states that energy is neither created or destroyed. Since there is nothing to absorb the energy, it will only be reflected back. If we place what the literature calls “acoustic tile” on the wall, we now have a situation that the tile is denser than the air but obviously not as dense as dry wall. This offers us a change in density. Tracing the sound transmission path, we have air to tile and tile to wall. Therefore, less energy will reflect back and some of our higher frequency, air borne, energy will be absorbed. However, more of our lower frequency energy will be transmitted. How do we reduce these transmissions?
Abrupt Mass Change
We know that we need an abrupt change in mass to have an impact on our vibration transmissions and thus sound energy. Lets examine two different structures to illustrate our points. If we take a wall that has two sheets of drywall glued together and nothing in between and a wall with the same two sheets of drywall separated by studs, we have two walls that have the same mass, but the wall separated by the studs will have a higher sound transmission class number holding back more sound energy. The wall with the studs contains more changes in mass or density for our vibrations to travel through.
In our two pieces of drywall only example, sound energy strikes our wall and then travels quickly through both walls. In our wall with the studs separating the two pieces of drywall, we have an air space between the two pieces of drywall. Incidentally, we can make that structure even more effective by filling the air cavity between the drywall panels with a fibrous material such as mineral wool or fiberglass insulation. That’s because the cavity between the drywall sheets will resonate, and friction of the vibrating air against the fibers will produce heat. We can’t actually destroy the energy, but we can turn it into non-acoustic form.
Either wall structure will work well when we consider lower frequencies. In both of our wall examples, the drywall will have to be nailed to studs for support. It would be great if we could figure out how to have them “float” in space without any attachment points but that is not realistic. The drywall sheets nailed to the studs, will form a solid entity which is a road for lower frequency energy to travel upon. Even though the two walls are different because of the air space, they are both viewed as a solid entity by longer, lower frequency energy.
Sound travels through mediums. Air is a medium and so are the physical materials we use to build our home theater, personal listening rooms, and professional recording studios. To soundproof our structures we must use mass that is arranged in a specific manner in order to reduce vibrations. It is the vibrations that produce sound energy and proper structure vibrational management is critical if we are to have any success at the soundproofing task. In part two, we will discuss more on vibration and damping.
Sound treatment and soundproofing are terms that have completely different meanings. Both terms share some of the same physics to arrive at their meaning, but both have completely different acoustical objectives. However, I can tell from the questions that I receive from customers, that the meaning of sound treatment is mistaken for soundproofing and the […]
How to soundproof a recording studio can be broken down into two main parts. First, we have the recording environment. Is it for recording vocals, drums, choir, a band? What will the sound-producing sources be that will be recorded? The second part is the monitoring or playback environment. Is it the mixing, control, or editing […]
This Blog has been updated from it original posting to reflect new information and changes in technology regarding how to soundproof an apartment. Updated on 11/26/19
Working out how to soundproof an apartment sounds like a daunting task. It is not easy. With paper-thin interior walls and noise generating people living above, below and to the sides of you, it is not easy. Our soundproofing must also be portable and mobile, so after we get kicked out, we can take our stuff with us. Let’s backtrack a bit and see if we can figure out how to soundproof an apartment without getting evicted for excessive noise.
Identify And Measure
First, we must decide who or what is making the noise and how much of it we have to soundproof for. We must quantify and qualify each frequency along with its amplitude or strength. Is it our neighbor to the east that is playing his stereo at certain times of the day. Is it the family below with the home theater system that has more subwoofers than acoustic sense. Is it your electric guitar playing or better yet, how about drums? We need to identify what source and level we are dealing with no matter if it comes from inside our apartment or outside.
Putting A Number To The Noise
After identification, we now need to determine what our sound pressure issues are. Place a Db meter within your room at the quietest part of the day. Do the same for the loudest part of the day. Record this information. Measure outside your room to find the level of the noise outside our room. Pick the loudest part of the day and what you think is the quietest part of the day or night. You will have to set your alarm clock for this test. Once we have both numbers or sets of numbers, we can decide what method in our bag of tools on how to soundproof an apartment.
What Do The Numbers Mean?
What is the difference between the two sets of numbers? Let’s look at the outside low to high representing the noisiest and quietest times we measured. Was the pressure reading at 85 SPL during the loudest outside? Was it, say 60, during the quietest. Was the inside measurement, say 50, at the quietest which was probably 2-3 in the morning and maybe 80 at the loudest when you were playing guitar. If we want the quietest within our room, we must stop 35 decibels of sound energy from the outside during the loudest part of the day for the quietest part of the day inside our room. Each dB of energy costs money.
We Are The Noise
For illustration purposes, let’s take the path of least resistance and the path that we have the most control of. Let’s say we are making noise from whatever the source and we want to protect our neighbors from it, so we do not get thrown out. The very first thing we must do is turn down, talk lower, and play more softly. Don’t like any of these options? That’s all good. You want to play louder passages and sing rock and roll. No worries. We will just build a new room within your apartment, just kidding. It is an ideal approach but it would have to be designed so that it was self-sealing, think of sound like water, and it would have to be assembled and then disassembled when you moved. Don’t forget about the additional weight upon the apartment exterior and interior structure. A room within a room is ideal acoustically but not practical in our discussion of how to soundproof an apartment. If we turn down in all areas, we can focus on the inside surfaces of our room as a start.
Excess energy from within our room can be dealt with using sound absorption technologies. If we have a low end or low frequency generating device in our room, we can use low-frequency, sound-absorbing devices. The smaller our apartment, the more we need to make it smaller by adding low-frequency sound absorbers. With the wall surfaces of our apartments, we could use acoustic foams to absorb excessive middle and high frequencies.
Sound Absorbing Foam: https://www.acousticfields.com/product/acoustic-foam/
Furniture And Drapes
Reflections from our room wall surfaces can be treated with sound-absorbing materials to reduce the strength of the reflection and help us to lower the overall room reverb times, so our vocals and instruments can be heard clearly without trying to pull them out of some sonic soup. Draperies can be used or open-celled foam acoustic panels can be color coordinated into the decor of the room. Furniture can be placed at least the large cushion sixes for lower frequency control above 100 cycles.
Acoustic Panels For Apartment: https://www.acousticfields.com/product/acoustic-panels/
Drums And Bass Must Move
If you are going to play sound sources with bass drums and guitars, you need to move. There is simply no way to treat your room to manage the noise to your neighbors without building another room which is mechanically decoupled from your apartment at every mechanical connection. The floor must also be separated from your existing apartment. It is best with these instruments to get a free-standing structure away from other people.
Sliding Window Panels: https://www.acousticfields.com/product/sound-absorbing-panels-for-windows/
All In Control
We can control the noise levels within our rooms and certain instruments are just not practical for apartments because so much new construction is needed. Work within yourself and the surfaces of your room to control reflections and either add lots of thick soft furniture or build low-frequency absorbers that can be tuned to your room for maximum performance.
I hope this explanation helped. Please leave any comments below so I can get back to you. Don’t be afraid to hit those Facebook like, Google+ and Twitter buttons on the left hand side so other people can see this post. And if you want to learn more about this subject please sign up for our free room acoustic treatment videos and ebook which provide step by step instructions. Get instant access by signing up now.