All about recording acoustics

The study of recording acoustics is a fascinating but intimidating study. However, we'll break it down into several principles that can be applied to help the bedroom recording studio function properly.

Here's the course of action: we split the subject into two topics as it relates to the studio, sound transmission and sound reflection. We'll discuss how they are relevant to the recording studio, and then ways to implement them.

Since I am not a recording acoustics expert and have only worked on one studio (my project studio), I will hand the ins and outs of retrofitting a studio for proper acoustics to people who have more experience. In other words, I'll give you links to research the matter further. :)

Very simply, recording acoustics is the study of how sound works - looking at how sound waves bounce or pass through different objects and what amplifies or attenuates (diminishes) them. How does that affect the recording engineer? In several ways.

  • First, you have to worry about sound coming into the studio from outside.
  • Second, you have to think about the reverberation or "sound" of the room, if it has flutter echo, long decay, nasty decay, etc. (Decay is the reverberation of a sound after the original sound stops until it dies away.)
  • Finally, you might have to think about others outside the studio who might not want to hear what's going on inside. :)

#1 Sound Transmission

If you've done any kind of recording, you will have some sort of noise on it, likely from some external souce. It could be rain on the roof, birds singing outside, an air conditioner downstairs, or footsteps overhead. Any way you dice it, noise happens. That is half the reason that recording studios are so concerned with construction and using the right materials.

Everything transmits sound to some degree. Sound is vibrations (something you can feel at lower frequencies), and it is transmitted by transferring the vibrations to surrounding air or materials. When a sound wave encounters an obstacle its energy is split two ways - some of the sound is absorbed and transmitted by and through the object, and the rest is reflected back by the surface. However the denser the obstacle (or wall) is, the less it will transmit, or the more it will absorb.

Our job is to find and place materials in the walls of the studio that will absorb as much sound as possible. There are various materials used, from concrete to drywall, in the walls and floor, as well as different strategies in using them, like building a double wall, hanging two layers of drywall, and filling the wall with insulation.

I prefer to focus on simply recording, which keeps me busy enough. But when I built my project studio I researched somewhat extensively online on the proper principles to use in constructing a studio. I'll include a few that were helpful to me below in section 3. Check them out - they have a lot of good info to absorb.

#2 Sound Reflection

The second part of our survey of recording acoustics deals with the way sound behaves in rooms. In the first part we looked at how sound is transmitted through obstacles, but that is only half the story. When a sound wave encounters a barrier, some of the energy is transmitted and some reflected.

If you don't believe me, cup your hands to make a tunnel from your mouth to ear, and shout something really loud. As you recover your hearing, let's think about what happens to the sound. It is reflected many times over until it reaches your ear, and it was still quite loud when it got there.

It's that way with a room as well. Whatever you sing or play is reflected off the various walls until it simply loses energy and dies away. Normally this happens with in a second or two, unless it's in a big room (like a cathedral). However for recording we don't want such a large reverb (usually). If it is a big decay time, we have to tame it down somehow.

There are a multitude of ways to achieve this, both cheap and expensive to varying degrees of success. You can put carpet on the floor to absorb the high frequency sound, or put curtains up. This can help some, but most common materials combat high frequency sound, while leaving the low stuff run free. We need some solution to take care of the wide band problem.

Fortunately, some relatively simple options exist. Acoustic foam comes in various shapes and sizes, and even does bass trapping. That is the simplest, most effective way for a small studio/room to get acoustic results.

I can't profess to know all about recording acoustics and solve all the problems. However, others can, and I can point you to them. Stay tuned for part 3.

#3 Links

OK, I've bored you enough with my less than exciting attempts at explaining recording acoustics to you. Here I will pass the baton to other websites that have gone this road before, and done a much better job.

If you are building your own space or renovating a room, be sure to check out www.acoustics101.com. They have an excellent book on building a room, and what to think about in the structural elements of things. They refer briefly to Auralex foam products for the sound reflections (#2) part of things. I use Auralex products, and am well pleased with them. They offer a wide range of treatment products, from various thicknesses of foam to bass traps and isolation platforms. Check them out at www.auralex.com, or look at some of their products at zZounds.com or at FullCompass.com.

When I was building my project studio I referred to acoustics101.com a lot, and took a lot of ideas from it. Maybe I can describe my studio later, and what all I used in making it.

Another article I found helpful is arts.ucsc.edu/ems/music/tech_background/TE-14/teces_14.html. It has a description of the principles of acoustics, and goes on to talk about practical application of them in an actual room in a house, a bedroom recording studio if you will.

Do you have a link that should be here? Please give it to me, and if it will work for here I'll add it so everyone can benefit.

#4 Conclusion

This is meant to be a brief (and Very Brief!) introduction to recording acoustics and the recording studio. I just want to get your feet wet, so you can study everything for yourself. The web has a lot of good info available, and this page is designed to help you get started.

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