We all know that however good your monitors, however great your interface, plugins and outboard, if your room isn’t sorted you’ll really face some challenges getting a good mix. So why do so many of us not have even basic acoustic treatment?

The Biggest Problem Is The Hardest To Fix

The nature of the problems presented by poor acoustics is easy to understand. As well as travelling directly from speaker to ear, sound bounces off the walls, floor and ceiling and this reflected sound colours the direct sound. The problem is that the solution can get complicated and this is partly due to there not being a single issue which needs fixing.

We all know that in typical sized rooms the biggest issues exist in the low end. These issues are most difficult to fix. It’s understandable that many people, when faced with what seems to be a bottomless pit of complexity and potential expense, disengage and reach for their headphones…

This is a mistake. There are two categories of issue. One is hard to fix, the other is simpler. Does it follow that if you can’t fix the whole problem you shouldn’t fix any of it? We’d suggest that there is a happy balance to be struck based on your situation and budget.

Velocity Vs Pressure

One of the biggest issues is one of understanding. The issues which present themselves below around 125Hz are different to the issues which occur above that frequency. Sound has two properties - velocity and pressure. The peaks and troughs of a sound wave represent the points at which the air molecules are changing direction. They briefly stop moving and these points represent the point of maximum pressure and minimum velocity. Conversely the point at which a wave crosses ‘zero’ represents the point at which the pressure is the same as the ambient air pressure but also the velocity is at its maximum. There is a 90 deg phase offset between these two properties as when pressure is at its maximum, velocity is at its minimum and vice versa.

Understanding The Problem

This is related to the issues facing room acoustics because of the existence of standing waves. To experience these just put on a sine wave at a suitably low frequency (try 80Hz) and walk around your studio. You’ll soon find a place where the audio drops dramatically. Move away and you’ll find the level increases hugely. You’ll also find a big rise in level at the walls and in the corners. These are standing waves and at the walls the velocity of the air molecules, by definition, is at zero. It has to be because there is a wall in the way!

Below around 125Hz the behaviour of sound in rooms is dominated by pressure. Above around 125 Hz the behaviour of sound is dominated by velocity and behaves in a more ray-like manner. This is intuitively a more easily understandable behaviour. Advice about placing absorption at reflection points is exactly the kind of treatment aimed at issues in this area.

So we have two types of issue with two types of solution - bass problems with difficult, often expensive solutions, and issues higher up the frequency range which are relatively easy to fix. As long as you don’t use techniques and products designed to fix issues for which they aren’t designed there should be appreciable gains.

Using Acoustic Panels “Wrong”

Acoustic panels absorb energy. For them to do this they slow down moving air molecules. The lower the frequency intended to be absorbed, the longer the wave and the thicker the panel has to be. Adding a relatively small amount of absorption can have a significant impact on sound in the room but adding more and more treatment in the hope of affecting an issue for which the product isn’t designed to act isn’t going to work. Covering 100% of the wall space in a studio will absorb down to the cutoff frequency of the panel but will leave frequencies below that unaffected, resulting in an imbalance in the response of the room, usually an excess of lower midrange and bass.

The important thing when addressing acoustic issues is to keep in mind that a balanced approach is always best. Ideally we would all be working in purpose-built studios with carefully designed acoustic treatment with speaker calibration tech such as a Trinnov or Genelec’s GLM system or a software solution like Sonarworks Sound ID to make that great room even better. However for all sorts of reasons most of us can’t do this. Budget is of course a huge reason as is the fact that so many people rent their studios and homes and often can’t even attach a wall panel without incurring the wrath of their landlords. However, many of us who can use acoustic treatment don’t because we feel that if we can’t fix the bass, why fix anything?

So Do Acoustic Panels Really Work?

In short, yes. Well designed acoustic panels do what they are designed to do. The issue is that people often expect them to fix an issue of a type that aren’t designed to fix!

There is a balance to be struck here and in this video from Studiospares there is a nice demonstration of what can be achieved using off the shelf absorbers. It’s aimed as much at home offices as it is studios (though I know my studio is as much an office as it is a studio so there is often not much of a distinction to be drawn). By introducing panels into a room during the video you can hear the effect and while there are more sophisticated approaches out there, this off the shelf approach is still very worthwhile.