How to silence a computer

While we love our PCs, we don’t always love the noise that comes with them. What can you do about it?

This time we’re not going to look at the production of sound, but rather stopping it – seeing just what it is within your PC’s case that’s making all the noise, how the nature of sound affects what you hear from your PC, and the techniques to silence it.

In short, sound is a waveform that propagates through matter. More distinctly, and as we frequently know it, sound is compression waves – generated for example by a source that vibrates, such as a speaker cone – that travels through any substance that can conduct its energy. As a waveform it has properties such as frequency, wavelength, amplitude, intensity, and speed – and we can measure the propagation of sound by how fast it travels.

Different materials conduct sound waves differently. Solids, and especially metals, can comprise tightly packed molecules that conduct sound very well, which is why you can feel vibrations on train tracks while the train is miles away. But density isn’t a defining factor; atomic structure plays a role. Lead is dense for example, but an excellent sound insulator. Technically, compression waves that conduct into a solid can become transverse waves. The difference between compression and transverse waves is that compression waves are fluctuations of equilibrium pressure in substances like gasses and liquids, where molecules can move more freely, whereas in solids the wave energy can also be conducted through what’s known as shear stress – energy conducted along and through a material, instead of against it.

Liquids and air are less effective than solids, and temperature plays a role too – cold air conducts sound slower than warm air, for example. In fact, as you can see opposite, a solid like Iron conducts sound some fifteen times better than air, and even water is five times more effective. This means it also travels further, and is why sea creatures that rely on sonar can sense over very long ranges.

Hearing sound is a similar principle to generating it: in its simplest form, vibrations in the air reverberate a membrane in your ear, which reverberates tiny structures inside the ear culminating with the cochlear nerve which, in turn, translates this to electrical impulses for the brain.

As they travel waves get weaker, with their amplitude or ‘loudness’ decreasing as a square of the distance from the source, at least in air.

In the absence of matter through which to propagate, sound waves cease – which is why there’s no sound in the vacuum of space, despite what just about every sci-fi movie or TV series would have you believe!

When it comes to sound generated by our PCs, which we generally refer to as noise because we don’t like this particular type of sound, there’s not much we can do about distance, as we frequently sit so close to the source. However there is plenty that can be done to reduce or absorb noise before it reaches our ears.