Every day, we experience a symphony of sounds to make our lives richer. From soothing sounds to less-desirable noises, the auditory stimulus around us is vast and elicits a specific response in our minds. SAS International’s Stuart Colam, an acoustic engineer, explores the ‘what, how and why’ of sound.

If air was visible then it might make it easier to explain, but sound is essentially bits of air vibrating. These air molecules vibrate and bump into each other, which, in turn, results in a local increase in air pressure. This chain reaction happens quickly. For sound to be produced, something needs to make the air molecules move. When this occurs and the molecules bump into one another, an increase in pressure commences, as the molecules are essentially being squashed together and passing on vibrational energy, molecule to molecule.

The movement of air propagates; that’s what we call sound. The increase and decrease in air pressure of the molecules bumping into each other creates a push and pull of sound waves. They reach your ear and vibrate your eardrum. Your brain interprets this as sound.

Sound travels at different speeds depending on the medium. In steel, sound travels 17 times faster than in air, while in water it travels about four times faster.

In the built environment, sound is sometimes overlooked and should be an important consideration. When designing modern interiors there is much more than meets the eye – we must consider the ear as well. This issue is becoming particularly important due to the proliferation of open and agile working environments. Sweeping interiors are prominent in today’s commercial buildings, therefore demand is growing for ceiling designs to suit these interiors while still controlling sound travel. It’s why metal ceilings have become the go-to solution that ensures these open-plan designs are not jeopardised by noise levels.

A client might well place greater emphasis on aesthetics, but a good design must deliver effective sound management and an acoustic landscape which positively impacts on the productivity and wellbeing of building occupants.


Stuart Colam

Acoustic engineer, SAS International