Sound Absorbing Information
Basic information about sound absorbing, sound proofing, and sound diffusion for people who are interested in making their work or play space sound better through the use of sound absorbing materials or artistic wall panels (such as Wedgewalls).
The Makers of Wedgewalls obviously encourage everyone to use sound absorbing panels that are artistic in design, effective in application and look really cool! There are thousands of sound absorption materials out there. Hopefully, this site will help you find the sound control method that is right for you.
Absorption (acoustics)
Sound Absorption means the absorption of sound waves by a specific material or a combination of materials. The amount of "Absorbed Sound" can be referred to as the difference between a sound that is transmitted from or through a hard, flat, surface vs the same sound being altered by an absorbent or non-reflective surface.
In a nutshell, a material or surface that absorbs sound waves will not reflect them. Absorption of a given material is frequency-dependent and is affected by the shape, size, location, and the way it is mounted or affixed in an area, wall or room.
good sound absorbing materials are usually porous. Mineral wool, glass wool, and micro perforated plates work well as sound absorbers. Absorption is not a single mechanism of sound attenuation. Propagation through a heterogeneous system is affected by scattering of sound waves as well.
Acoustical absorption is different from sound diffusion. Wedgewalls sound panels do more for sound "Diffusion" than they do for sound absorption - although, some sound absorbption can be attributed to wedgewalls, or a well-placed array of artistically pleasing wedgewalls sound absorption and sound diffusion wall panels can actually do a good deal of sound absorption along with sound diffusion.
The most common misconception about sound quality (or misuse of definitions)
I'd like to point out a BIG misconception – the is a huge difference between "soundproofing" and "sound deadening" or "sound diffusion". Soundproofing is what people do when they don’t want anyone to hear the sound pass from one room to the next. Sound deadening or diffusion is what you do when you want to stop the sound from bouncing around inside a room.
You can have a soundproof room that sounds like an echo chamber on the inside, but a person can barely hear a sound in the next room! You can have a room that is completely “Dead”, where you don’t hear any echo sounds or reverberation inside the room where the sound is being created, yet you can hear the sound just fine in the next room. Typically, a room that has been treated for "sound deadening" or "sound diffusion" is a room like a recording studio or a home theater where you don’t want the room to have any “echo” sound. Sound diffusion or deadening accomplishes 2 things. It enables a listener to hear the sound that is coming from a musical instrument or speaker system ONLY - as opposed to hearing the sound come from the instruments or speaker AND THEN bounce off of the walls, ceiling, floor and windowsb ack to your ears. Have you ever been in a big, empty basement with concrete walls and floors? In a hard room you can hear the sound bounce off all the hard surfaces and back into your ears – this is called “Natural Reverberation”.
But what is reverb? In order to understand the answer to this question, it is best to start out by explaining what is an “Echo”. Let’s say you stand at the edge of a cliff and shout at the top of your lungs. The soundwave from your vocal chords travels a great distance, bounces off the cliffs at the opposite side of the canyon and comes back to your ears. In extremely simple terms, that’s an echo.
But, by the time the sound travels across the canyon and makes it back to your ears it’s lost a lot of energy, so it’s quieter. And, it’s traveled a long way, so it’s taken a few moments to make it back to your ears. So why did the sound come back to your ears quieter than when you originally shouted at the top of your lungs? There are a couple of reasons: 1. The sound traveled through the air as a big, invisible wave of vibrations. Like ripples in a pond. The farther the sound traveled, the more the air around you absorbed the energy from the sound wave vibrations. And 2. As the sound bounced off the opposite walls of the canyon, the various angles and densities of the canyon walls diffused much of the sound.
So what does this have to do with “Reverb”. A reverb is a whole bunch of really fast echoes all happening really close together and at different speeds. When you clap your hands in a square room, the sound comes from your hands, through air, bounces off the closest wall and back to you ears. But, at almost the same time, the sound also bounces off the next furthest wall and back to your ears. Because the next wall is a little further away, the sound takes a little longer to get back to your ears. You can repeat this process of sound coming from your hands and bouncing off the walls, the floor, the ceiling, the doors, the windows, the furniture, and everything else in the room – all at different lengths of time and at different levels because some surfaces are harder than others, some are closer, farther, and some things in the room might be very porous and not reflect the sound back to you hardly at all.
When you are in a cave, this is the perfect example of “Reverb” because the walls, floor, and ceiling are all very hard and reflect the sound back to you without much diffusion. Also, a cave has lots of different shapes and sizes so the sound con bounce back and forth between all the reflective surfaces unimpeded and your ears get to enjoy the fun the whole time! The main difference between an “echo” and a “reverb” is the duration of time between the moments a sound is created, and when you hear the sound being repeated.
A person normally refers to a sound repeat that takes more than 1/10 of a second as an “Echo” and a sound that takes less than1/10 and send to be repeated is a reverb. I’ve seen it written that the definition of reverb is as follows: Reverb “characterized as random, blended repetitions of a sound occurring within thirty milliseconds after the sound is made.” Personally, I think 30 milliseconds is way too fast. I think 100 milliseconds (1/10 of a second) it’s about the cutoff point where the sound repeat changes from and echo to a reverb or vise-versa. But, the “Random, blended repeats of a sound” part I agree with completely.
Have you ever noticed that the harder or flatter the surface is that you are yelling at - the louder the echo is when it comes back? Or, did you ever notice when you are sitting on a fishing boat on the lake when there is no wind or waves, you can hear a quiet conversation that 2 people are having in a boat on the water 300 yards away? That’s because the water makes a perfectly reflective surface for the sound to travel unimpeded. But let’s say you add a little wind or a few waves to that lake, and what will happen? The sound won't travel nearly as well because the wind and waves will absorb the sound -or diffuse the sound. In other words, you are breaking up “Diffusing” the sound waves and impeding their travel from point A to point B.
When I am sitting in my home theater, I don’t want to hear the sound from the TV speakers bounce off the ceiling, floor and the back wall, echo all around the room and make my TV sound like it’s in a cave. That makes it very hard to understand what I’m hearing!
I also don’t want the sound of the home theater to be totally dead or diffused either. You want the sound of the room to have a little life, but not sound like a stiff, cold basement.
Also, too many echoing /reflective angles can create spots in the room where the sound seems to go “Dead” this is called “Standing waves” – where the sound waves interact negatively with each other and seem to cancel each other out. Standing waves are a whole other sound wave/sound room phenomenon - we'll discuss that more later on.
Another example of a time when you will want to use sound diffusion is when you are singing in your home studio and standing in front of a microphone, You don’t want the recording to sound like it’s been put through an electronic reverb all the time. If your room is too “Live” or has too many hard and reflective/flat surfaces, the room will have an echo or reverb type of sound in the microphone whether you like it or not. Most profession recording studios make sure that the sound of the room where the vocal mics are is very dead and diffused. That way, the engineer can add reverb or echo to the vocal track later, at their discretion and to their liking, as opposed to being stuck with an echo or reverberated sound all the time.
So let’s say I want to deaden or diffuse the sound in my home theater room or inside of my recording studio. One of the first things I want to do to “Deaden the sound” is to diffuse all reflective surfaces. This can be done in a million different ways that work very well. One way is to cover the walls with egg cartons, carpet, cloth, foam (the thicker the better) and lots & lots of thick, porous, surfaces and odd angles. The more you add – the more dead the sound inside the room will be. AND the “Drier” it will sound inside the room.
NOW all this sound deadening does very little for keeping sound from getting outside the room. Why, because sound diffusing/deadening is NOT soundproofing.
If you want to keep the sound from passing outside of a room – that is “Soundproofing” and soundproofing is in-essence, an entirely different process.
