Acoustics for Project Engineers Part 1  ONE

Part 1: The basics, location

If you know a lot about acoustics, stop here!

Some project engineers and managers, who have to get studios built, know a lot about acoustic; others very little. (Why pay a dog and bark yourself?) But please don't feel insulted if this tells you what you already know!

This guide doesn't try to tell you how to design a studio. Its aim is to help you "speak the same language" as your consultant, and so, hopefully, get the best out of him or her.

Does a project manager need to know anything about acoustics?

Maybe not. You could go to a studio designer and simply ask them to design a studio suitable for your purpose. If the designer is a reputable one you could well end up with something adequate.

But the compromises between cost and performance might not be the best for your particular purpose. Perhaps your space is not large enough for the multiple walls and sound lobbies that the consultant wants, or the floor loading is too low for the weight of a full studio construction. Or your budget just doesn't run to the construction that your designer thinks that you ought to have.

Something of this sort, after all, is the rule rather than the exception. That's why it's useful to have an idea of what those figures in the specification really mean - and what are the implications of changing them to fit in with your own practical circumstances.

Some of the discussion below may offend purists as it skates over detail. There are some excellent acoustic text books and I have no intention of writing another!

What must a studio do?

The structure of a studio has to provide two things:

1. Sound isolation. It may need to keep in the noise that you are making, to avoid annoying the neighbours, or to keep out the noise that your neighbours are making, or both.

2. The right acoustic environment for the sounds you will be making.

As well as this, all practical studios must have mechanical ventilation systems, and this inevitably produces some noise. So the specification of the ventilation noise is part of the studio acoustic specification.

The fundamentals - location, size, shape, layout

Some of the most important decisions affecting studio acoustics are often made before an acoustic consultant appears on the scene.

Location and layout

Choosing a quiet location is obvious. But what may be forgotten is the effect of ground vibration or structural vibration in a building.

The sound produced by vibration may not be obvious or even audible before the studio is built, because it is hidden ("masked") by the general noise of the surroundings. This can be a particular problem if you're trying to build a cheap and simple studio. When the studio is built, its walls will keep out the general noise. But vibration will not be kept out by a simple construction. The reduction in the general background noise may make it quiet enough for noise produced by vibration to become a nuisance.

Typical sources of vibration are rail lines and refrigeration plant. Ground vibration or building vibration can be a problem even for studios that have a proper "fully floated" construction, where the whole studio is a solid and heavy box resting on springs. The moral: if in doubt, get the location checked out.

But before you spend money, do the following simple exercise. Stand in the location of your studio (or, if the building does not exist, use your imagination), and take a notepad. Look to the left. Write down what will be in that direction, and what activities may either cause interfering noise, or may be interfered with by the noise that you make. Repeat this for the other five directions: right, front, back, up and down. Make a note for the file. If you really try not to leave anything out, it's surprising what can come to light in this sort of formal exercise, that otherwise may easily be overlooked.

Note which places will be sources of interfering noise to you, and which places will be most sensitive to noise you make. If you may be making a loud noise yourself, decide which places it is most important to protect from interference. Neighbours not in your own organisation will usually come first - if you annoy them enough they could possibly involve you in expensive legal proceedings.

A simple change in layout can save trouble and money:

Bad layout

With this layout it is difficult and expensive to achieve enough sound insulation to avoid interfering with the neighbours. That's why there's a red cross through it!

By changing the layout so that the corridor is between the studio and the party wall, the studio construction could be made lighter and cheaper.

Studio size and shape

One of the most common questions that acoustic consultants get asked is "What shape should I make my room so that it will sound good?"

For a long time it was believed that certain shapes had special properties. In fact there are no perfect shapes, although there are some bad shapes to avoid.

The simple answer is, make rooms as large as possible, as large rooms usually sound better than small ones. Apart from that, you should certainly not have any two main dimensions in the ratio 1:2 or 2:3. However don't worry too much about this, as you can usually avoid exact whole-number ratios by a small tweak to the design. (By the same token, make sure the room shape doesn't get tweaked back to a simple ratio at a late stage in the project.)

Avoid long and narrow rooms: they tend to sound "coloured".

Usually you do not need angled walls. But you have to use them sometimes, where it's impossible to avoid having hard surfaces opposite each other. It's a superstition - nothing more - that non-rectangular rooms are always better.

Don't be surprised if you see other "rules" for size and shape. The requirements vary depending on the size and the purpose of the room. The above applies to normal sized studios but not, for example, to concert halls. Continue


Phone or email for a free initial discussion about your project.
Phone 020 7624 2512 or click to contact us.

Text charts and images copyright Tony Woolf 2000 & 2007 unless otherwise stated.