Soundproofing a room means that we want sound energy that is created in the room to stay in the room and we want sound energy that is generated from outside the room to stay outside our room where it belongs. In order to soundproof effectively, we must address the floors, ceilings, and walls.

Sound Proofing Sealing Process

First, we must seal all openings in the room, no matter how small they are. Openings around light fixtures, electrical outlets, door edges, moldings and window trims. Use a sealer that is silicon based and will seep into the crack or opening and form a complete seal with all edge surfaces involved. Apply the sealer during the warmer temperatures and let it dry thoroughly. Return and reapply to any areas that have recessed during the drying process.

Walls First

Wall thickness is our friend when it comes to soundproofing using our walls. It does not have to be solid, but as a general rule the thicker the better, up to a point of diminishing returns. It depends on how much sound energy is generated in the room we have to keep in the room and how much sound energy is generated from outside the room that we have to block out. It is also about the way we arrange the materials in the wall. Now we are in the area of vibrational acoustics where we have to control the vibrations from one layer of the wall to another layer of the wall. An example would be a 1/2″ piece of plywood with a vibration damping material applied to its backside and then attached to a 1″ piece of multiple density fiber board. This arrangement provides three different materials for vibrations to have to go through and by doing this they lose their intensity or energy. Remember, vibrations produce sound. Do we need more layers to our wall? It all depends on usage and sound pressure levels. Careful sound pressure measurements are a must both inside and outside the chosen room over different time periods and different usage loads, and give one a starting point for material selection and wall thickness.

Don’t Forget the Ceiling

Ceiling structure for soundproofing is similar in design and composition to our wall technology. One particular soundproofing method used is to decouple the ceiling from the rest of the structure by building another “ceiling” and then decoupling or in common language separating the new soundproofing ceiling from the existing ceiling with isolation clips and airspace. Yes, airspace is another material that we can use to reduce vibrations with. If we decouple the new soundproof ceiling from the existing ceiling and leave an air space between the new and old, we have effectively created an isolation barrier technology and a low frequency diaphragmatic absorber which also absorbs bass energy.

Floors and Ceiling

Our floors are just like our ceiling and we must decouple the new soundproofing structure from the existing floor. We float the new floor over the existing floor and use isolation pads to place the new structure on. The rigidity and construction of the floor system can also contain a calculated air space which can absorb internal bass energy. Any decorative inside the room treatment can be added, and thickness is our friend most of the time when it comes to keeping sounds inside, in and sounds outside, out.

Not Easy Or Cheap

Soundproofing a room is not easy and to do it well is not cheap either. One must first determine how much a noise issue one has and then what is our budget available to deal with this issue. Most of the time, the noise problem can not be resolved with the existing budget and one has to re think the amount of solution versus available dollars and make it go as far as it can and accomplish as much of the noise objective we can. One can do it in steps over time to achieve the desired results.

We have all heard really loud sounds. A jet taking off, a dragster or funny car blasting away from a dead stop, or an explosion all generate large amounts of sound energy. The perceived loudness of this energy by our ears depends on the particular frequency we are addressing and the intensity at which we perceive or hear that frequency. To interpret this frequency/intensity ratio and put it in a form that more closely resembles actual human hearing, we go to what is termed the Fletcher-Munson loudness curves.

The Fletcher-Munson curves take frequency and intensity and apply this data to a predetermined domain of measurement. The Fletcher-Munson frequency start point is 1,000 cycles. The F/M loudness scale determines that the ear is the most reactive in the frequency range that starts with 3,000 cycles and goes through 4,000 cycles. This loudness scale also shows that the threshold of hearing is more reactive at lower frequencies. For example, the threshold of hearing at 60 cycles is 48 db higher than at 1,000 cycles.

Loudness of any sound is a ratio of the perceived magnitude of that sound energy by the live organism it encounters. The units or intervals the loudness scale uses must reflect real human reaction points. The units on the scale must match common human hearing experience and also match the sensation magnitude. The scale also must be constructed so that when the units on the scale increase by a certain factor the sensation magnitude of human hearing increases proportionately. If the units are quadrupled then the corresponding human hearing sensation must also quadruple.

Pitch is defined as frequency that reacts with the medium in which it is transmitted in. When sound travels through the air in a room, we have the frequency produced by the sound source and we also have that frequency reacting with the air and producing another sound. It is source sound and air sound combined. Pitch is not an objective quality but rather a subjective one. Pitch is the subjective quality humans assign to a sound in order to place it in its appropriate position on the music scale. There is a measurable difference between frequency and pitch.

Harry Olson wrote a book entitled “Acoustical Engineering”. It was published in 1991 but with only a new introduction from a 1957 original publication. The book “Acoustical Engineering” was based on an earlier work entitled, “Elements of Acoustical Engineering” copyrighted 1940 and 1947. I like to look at older acoustic books and read what the current thinking was at the time. It is amazing how some things have really changed and some things have not at all. I like one section entitled, “Orchestra and Stage Shell”. It talks about acoustic treatment in outdoor theaters.

The article focus states, “When orchestra and stage productions are conducted in outdoor theaters it is desirable to provide a shell to augment and direct the sound to the audience, to surround the orchestra with reflecting surfaces and to protect the performers and instruments against wind, dew, and other undesirable atmospherics” I like the use of, “undesirable atmospherics”. It is a nice way to say bad.

In this necessary “shell”, we must focus on the acoustical treatment that will line our shell with, in order to maximize the sound quality for all parties concerned. It appears from this section, that most of the shells in those days were concave in shape and design. This concave shape produced what the book calls, “intense and sharp concentrations of reflected sound in both the shell and audience area”. It also goes on to say that “these acoustic effects are particularly undesirable when the sound is picked up by microphones on the stage for sound reinforcement and broadcasting”. This reflected energy produced by this concave shell can not achieve a balance sound for the conductor’s position. Therefore, without the orchestra leader hearing what the audience hears, we have a definite acoustical issue when it comes to the treatment used inside our shell.

Poly-cylindrical shell or a concave shell lined with poly-cylindrical structures will produce the best sound for all parties concerned concludes this section of thought. It will be good at the microphone positions, the orchestra leader, and finally the audience. A poly-cylindrical structure is shaped by an 180 degree arch and then a flat surface for mounting. The arch is not a diffusor. It is a sound re-director. It uses the angle of incident equals angel of refraction physical law. Numerous poly-cylindrical devices installed in a wall, would redirect the energy that strikes them in different directions opposite to their original striking direction, thus creating a sound redirected sound field.

I have never heard a shell lined with poly-cylindrical devices, but I wish I could get that chance. Most concert shells I have heard are lined with quadratic diffusors which are usually positioned in both vertical and horizontal planes thus, providing two dimensions to our sound field which would be directed at the conductor and audience. It would be interesting to compare quadratic diffusion sound with poly-cylindrical sound just to hear the difference. It could be different in many ways.

With two dimensions of sound created by quadratic diffusors positioned both “vertically” and “horizontally” I would know that sound because I have created it on numerous occasions. It is characterized by a smooth and equal frequency spread across the room plane it is focused on. The diffused sound field would be equal parts “air” and equal parts sound. If it were a solid, it would look like a very loosely woven tapestry spread across a room boundary surface. I hope sound redirection through a poly-cylindrical lined shell retains this feature but adds something of its own. I do not know what that would be, but I would sure like to hear it.

What is Good Sound?

I walk through trade show rooms and listen to the exhibitors tell me what they consider good sound. They tell me their room is kind of their idea of good sound. Some tell me that their room sounds pretty good but does not fall into “good sound”. A hotel room is a compromise and one must work around many variables to achieve a sound that demonstrates what their product could sound like in a good room some say.

Some rooms have too much bass energy. Some rooms are bright and have so much specular reflections that it is difficult to hear all the vocals in a three part harmony or hear two bass instruments each producing their own sound.These rooms are characterized by low definition and a small image. Some rooms have the listening chair up against the back wall. Some say,”Our room will have the best sound of show”. Really?

I guess everyone has a different idea of what “good sound” is. Is good sound the type of sound where their is an emotional attachment immediately to the music? Is good sound the type of sonic presentation where one can hear every instrument and vocal in a balanced presentation? Is good sound the type of sound where the speakers and amplifiers disappear and one can only hear and “see” only the music? Is good sound a combination of some of these variables and not others?

For us, it is removing the room from the sound and having the ability to hear all the instruments and vocals in a balanced presentation.To achieve this objective, all low frequencies are heard without any bass bloat. There are layers to the bass and the bass attack and decay is as tight and clean as the attack and decay of middle and high frequencies. Middle and high frequencies are layered like our bass presentation and their is a distinct separation between the instruments and vocals.Comb filtering of middle and high frequencies is under control. Their is air present and instruments and vocals float in the room all across our sound stage. No speakers are seen or heard.

How does one achieve good sound? I am sure their are many approaches as there are opinions on what constitutes “good sound”. We choose to reduce low frequency pressure in the room from all low frequency producing devices. One must first deal with low frequency pressure in order for the middle and high frequencies to come through without being smothered by excessive low frequency energy. Excessive low frequency energy can be controlled at the source or at room boundary surfaces. Middle and high frequency reflections off of room walls can be controlled through the use and application of absorption or diffusion technologies.All of this control must be applied in a way that produces a balanced sound stage with a height, width, and depth.

A popular search term in audio is “db meter”. Sometimes people search for terms that they think go together or they have seen or heard it used somewhere. Sometimes there is a combination of words into a phrase that tries to illustrate an audio point or concept. Lets examine each word within the search term “db meter” and see if it the right word or group of words to use in this situation.

Db stands for decibels and is a unit of measure that those in the audio world use to describe intervals or amounts of energy within in a given environment. It is only that: a unit of measure. It does not have any value of its own other than to say it is a unit of measure that is calculated and formed to correspond to the human ear hearing range. A large db number can cause inner ear damage. A smaller db number may be too low to hear the difference in gain jumps. A db is part of a scientifically calculated scale or ratio for human hearing comparisons and even regulations.

What does the db unit mean when it is attached to a number? A db meter measures sound pressure levels.The sound pressure level can be assigned many different units of measurement. Therefore, using a ratio is better for human sense of hearing comparisons. A db unit is a ratio of acoustic power levels expressed in decibels that “comply” within our human hearing range. These are decibels that express a power ratio made for human hearing measurements. For example, a Saturn rocket has a sound pressure (Pa) of around 100,000 Its sound pressure level measured in db is 194. Normal conversational speech has a sound pressure of .02 while the sound level is 60.

Searching for a db meter may be confusing for the clerk at the store, sine we are really measuring sound pressure levels expressed in decibels in our room. Although, if you go to Radio Shack and ask for a sound pressure meter, they will search their product data base and will find no entries in it for “sound pressure meter” If you change your request for a db meter, they will have one for you quickly. It is funny how things work.

We have a client in Arizona who wanted us to build him a sound room with a living roof. A sound room you are all familiar with. A living roof may be an other issue. It was also a pleasant surprise for us.

A living roof is a roof designed to support 18″ of top soil and the watering and drainage system necessary to maintain this miniature ecosystem. Supporting 18″ of earth and water is no easy task, especially when the roof size is 25′ x 50′. That is 1875 cubic feet of earth at approximately 20 lbs. / cu. ft. is 37,500 pounds of earth, not to mention the piping for water and drainage. The roof must support 16 tons of earth and pipes.

Earth is an excellent barrier to external noise. Go into your basement and sit quietly. There you are surrounded on 4 sides by earth and concrete. In this project, the roof and 6′ up the 12′ side walls will also be covered with earth. So, in this project we have 1 1/2′ earth on the roof and six more feet of earth on each wall side. Now, we need concrete walls at the correct thickness to match the acoustical properties of 1 1/2′ of earth on the roof.

We determined that an 8″ poured concrete wall all around will meet all our structural issues for ceiling support and acoustical issues for sound transmission class ratings and all external noise measured calculations. The 8″ concrete shell will build a room that is 25′wide and 50′ long. The ceiling height is 12′. One could not ask for a better room size when it comes to acoustical issues that must be dealt with.

At 50′ in the length dimension, even a 20 Hz.wave, which is the lowest wave we usually work with in rooms has some room to run. No low frequency issues or any others for that matter when it comes to the 50″ length dimension.The 25′ width is also good for low frequency, but will give us a few issues. Those issues will be resolved through the use of our activated carbon technology which will be added to the inside walls. A ceiling height of 12′ only increases our room volume and is welcome for all forms of sound playback and recording.

If you spend as much time in your personal listening room as I do, you hear many different things and you become comfortable with the sound in your room because you have worked hard to get it to sound the way you want it to. I believe most of us set up our personal listening environments in a manner that allows us to hear as much of the music as we can. This attention to sonic detail helps us develop an emotional connection with the music.

One of the many things I notice is that when I enter my personal listening environment is that the outside world does not follow me into the room. It is almost like some type of force field that will not allow the energy of the existing and outside world in. This really becomes apparent when you hit the play button on the remote. If the “force field” is strong enough to keep out the outside world by just closing its door, it completes the job when music fills the room. What a joy to not think or hear anything but music; feel anything but emotion.

Sometimes on recordings that you have played over and over, you will hear a new sound. You know the recordings I mean. They are the ones that you know every pause or breath the lead singer takes and every note the guitar player uses on a fiery break. They are your comfort and go to songs when you really need to disconnect. Somehow, someway, you bend down to pick something off the floor and just as your ears move in a vertical plane down the speaker’s vertical axis, you, for a split moment hear something new. You pause, take a breath and reach for the remote. There it is again. Thank you, room !

Sometimes one can connect so well to the music that dancing and air guitar behavior occurs. Now, this is a real connection. It is a digital cable from your ears to your heart. It can be facilitated by time shifting your stream of consciousness through the use of intoxicating beverages. I don’t know why the volume is increased in direct proportion to the amount of fluids ingested. It seems to always be the case when you check the gain control the next morning. Perhaps beverages of this nature should come out with a warning label that states: Expect 10 dB increase in SPL for every 12 ounces consumed.

www.acousticfields.com

Room music is a search phrase that 368,000 people used last month in Goggle. It is an odd blend of words to search for and I really don’t know what the search objective was for those 368,000 individuals. Were they searching for a room to play music in with a sound system? Were they looking for a room to play music in with an instrument or vocal?

At Acoustic Fields, we hope all rooms are room music. Having a room that is designed to portray music in the best manner possible is a blend of both science and art. Science and the products that science creates can help deal with the two major issues of room acoustic management: room wall reflections and low frequency pressure. If one does not control reflections from all the room boundary surfaces, there is no chance of having any quality room music. Reflected energy arriving at our ears from all room surfaces, confuses our brains and any music created will go unappreciated. Without proper low frequency, energy pressure control, there will be no room music at all. It will be smothered and blurred to the point of creating interference in all frequencies in any music type presented.

Lets have room music in every room from now on. Lets use our science to create products that make every room a music room. Forget about living in the room. Lets have a room only designed for room music. It will be a room with amplifiers, speakers, and a music source to play room music from. It will have just two live beings in the room; a man and a dog. The man will be there to feed the dog. The dog will be there to keep the man from touching the equipment.

www.acousticfields.com