In December, Sydney will host one of the world’s largest acoustics conferences: Acoustics 2023. Thousands of academics, industry experts and acoustics consultants will descend on the International Convention Centre at Darling Harbour to discuss all things noise and vibration.
Sound is one of the main ways we interact with our world, and our ears are truly magnificent instruments. We can detect sounds across enormous ranges: volumes as small as 20 millionths of a Pascal up to 20 Pascal; and frequencies as low as 20 Hertz, such as the lowest note of a huge pipe organ, right through to high-pitched squeaks at 20,000 Hertz.
Acoustics are a key consideration in the design of buildings. Have you ever been in a cafe that is so loud you have to shout to be heard by the person next to you? Cafes often feature hard surfaces, which are durable and easy to clean but increase reverberation. Soft surfaces like carpets, curtains and soft furnishings absorb sound, but the best performance comes from glass fibre mats that can be placed behind perforated panels on walls and in ceiling cavities. A little more acoustic absorption would improve our experience of many cafes and restaurants immeasurably.
The exact opposite applies to concert halls where some reverberation is encouraged. Reverberation supports great operatic voices, as each beautiful note blends into the next. In these spaces, the acoustic design aims for the “Goldilocks” zone of just enough reverberation to create great music but not too much that other factors can spoil the effect. It is one of the reasons why the design of concert halls like the Sydney Opera House requires such great engineering skill.
And acoustic design is not just about making spaces as quiet as possible. If an office is too quiet then even soft talking from colleagues can make it impossible to concentrate. In this case, it can be beneficial to increase reverberation slightly or even play background sounds, so that individual conversations become lost in the ambient noise.
Speech privacy can also be important. Many of us live in apartments and terraces where we share walls with neighbours. Ideally, our walls need to block sound from travelling between rooms. Generally, heavy materials like concrete and bricks are effective at blocking sound transmission. If there is a cavity between walls then the sound-blocking performance can be increased further.
These are just some of the ways in which our daily experience is directly related to the work of acoustics specialists. All the more reason to welcome the world’s best acousticians to Sydney in December.
Dr David Hanson is a sound and vibration engineer who lives in Redfern.