The ancient myths and legends of soundproofing

David Mellor

David Mellor is CEO and Course Director of Audio Masterclass. David has designed courses in audio education and training since 1986 and is the publisher and principal writer of

Wednesday September 25, 2019

There is so much folklore about sound insulation, but the science and technology is easy to understand. Perhaps because it is expensive and difficult to achieve really good results, people look for 'magical' solutions...

There is so much folklore about sound insulation, commonly known as soundproofing, but the science and technology is easy to understand. Perhaps because it is expensive and difficult to achieve really good results, people look for 'magical' solutions.

Let's suppose sound insulation had never been invented. OK, let's now invent it - what do we need to do?

We need to prevent sound from passing from one space (your studio for example) to another (your neighbor's living room). Let's think about the possible ways we could do this...

If you can think of any other possibilities, apply for a Nobel Prize now.

The first option, absorption, sounds good in principle. However, materials that absorb sound are insufficiently effective. Light for instance is easily absorbed, so a photographic darkroom doesn't need a door - a folded passageway painted black will work just as effectively. It's a pity that nothing will work as well with sound.

This is perhaps the greatest myth of sound insulation. Absorption alone does not work, but it has its place as we shall see in a moment.

Creating an equal and opposite sound wave to cancel the original out actually does work. The problem is that it only works well for certain sound sources. For example a noisy piece of machinery can be enclosed, its sound captured, inverted and used to drive loudspeakers. This technique has also been applied to cars and aircraft. Perhaps one day it will be perfected for a wider range of sound sources, but the technology is not ready for the recording studio yet. Yes there are such things as noise canceling headphones and they work by cancellation, but the only way they could be used in the studio is for monitoring and it would be difficult to recommend working in a noisy environment and relying on them as a solution.

So, we come to the technique that actually does work - reflecting it back. It is easy, in principle, to reflect sound - simply set up a solid continuous barrier that possesses significant mass. Mass reflects sound - it's as simple as that. And every time you double the mass of a barrier, the degree of sound insulation improves by 6 decibels.

But what do you do with all that sound that is reflected? Surely that will cause a problem inside a well-insulated studio? Well yes it will, so you absorb it! This is the role of absorption - to dispose of the energy of sound that has been insulated by reflection. This is standard practice in almost every situation where good sound insulation is required. Mineral wool is a very useful material for this, and also is normally incorporated into a double-leaf partition to absorb sound that would otherwise reflect back and forth between the panels.

One last point - reflecting low frequencies is difficult as mass loses effectiveness by 6 dB for every halving of frequency. However, if the barrier can be made flexible as well as massive, or a flexible membrane incorporated, then low frequencies will be absorbed by the barrier bending. Here absorption does produce useful additional insulation.

Like, follow, and comment on this article at Facebook, Twitter, Reddit, Instagram or the social network of your choice.

Come on the Audio Masterclass Pro Home Studio MiniCourse - 60 great hints and tips to get your home recording studio MOVING

It's FREE!

Get It Now >>

An interesting microphone setup for violinist Nigel Kennedy

Are you compressing too much? Here's how to tell...

If setting the gain correctly is so important, why don't mic preamplifiers have meters?

The Internet goes analogue!

How to choose an audio interface

Audio left-right test. Does it matter?

Electric guitar - compress before the amp, or after?

What is comb filtering? What does it sound like?

NEW: Audio crossfades come to Final Cut Pro X 10.4.9!

What is the difference between EQ and filters? *With Audio*

What difference will a preamp make to your recording?

Watch our video on linear phase filters and frequency response with the FabFilter Pro Q 2

Read our post on linear phase filters and frequency response with the Fabfilter Pro Q 2

Harmonic distortion with the Soundtoys Decapitator

What's the best height for studio monitors? Answer - Not too low!

What is the Red Book standard? Do I need to use it? Why?

Will floating point change the way we record?

Mixing: What is the 'Pedalboard Exception'?

The difference between mic level and line level

The problem with parallel compression that you didn't know you had. What it sounds like and how to fix it.

Compressing a snare drum to even out the level

What does parallel compression on vocals sound like?

How to automate tracks that have parallel compression

Why mono is better than stereo for recording vocals and dialogue