Part I: Acoustics and why it matters
April 2021
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EAR TO THE GROUND
In this 3-part series, we will be exploring the influence and effect of sound in buildings, and how acoustics can be controlled and manipulated for optimal outcomes in specific environments. This week: acoustics and why it matters.
.webp "Unwanted noise | courtesy of freepik.com")
Noise is something that we are subjected to on a daily basis. Unlike our ability to focus our sight by turning our heads or looking away, pulling down a blind or switching on a light, sound is something that happens to us. Aside from plugging our ears with our fingers or covering them with headphones, we cannot choose not to hear something.
On top of this, with the advancement of technology, wireless innovations such as Bluetooth have meant that we can summon sound, on-demand: a heavy metal playlist to accompany a work-out, a cooking podcast to accompany a commute or white noise to help us nod off at night. Wherever we go, there is noise – wanted or unwanted.
The meaning of noise
Unwanted noise is commonly referred to as noise pollution, and is not always helpful in relation to the activity we are performing. Quite the opposite: it can be a nuisance. It distracts us from our primary hearing focus; a phone call, a colleague or indeed, no noise at all – silence. What one minute is our focus can the next become a nuisance, and vice versa. Trying to catch that song lyric and drown out the public announcement on the train platform? Or trying to drown out the song and hear when the next train is departing? The value of a sound is therefore relative and always experienced in context.
One form of noise pollution is what we know as background or ambient noise. This is the backdrop of sounds humming away behind meaningful sounds in our environment. For example, the fan on your desktop, a police siren outside, mumbled chatter coming from the room next door.
Noise pollution, aka unwanted noise, is what we are interested in from a design perspective. More specifically, how to minimise, downplay and control it in an indoor environment.
So what’s all the noise about?
Why does noise matter in the built environment? Well, there is a huge body of research suggesting that noise pollution and excess sound are problematic to human health, wellbeing and performance: from hearing loss to stress, cardiovascular disease, safety risks and disturbed sleep, unwanted noise can lead to a whole host of physical and mental ailments – not to mention how excess noise impairs communication between individuals in any setting. Reasons a-plenty, then, to design more harmonious, sound-controlled buildings. Indeed: the rules and regulations regarding exposure to noise have become increasingly stringent.
.webp "Harmonious building | Flotex Linear Complexity 550007")
.webp "school corridor | 433910 Sarlon Topography white")
Sound behaviour
Simply put, sound can take on one of two forms in a building: impact or airborne:
Impact
Impact noise is the result of physical impact to a building or solid material. The impact causes the building structure or parts thereof to vibrate, generating sound waves. An example would be footfall in a corridor or a door slamming.
Airborne
Airborne noise travels – as the name suggests – through the air. These types of noises can even become louder when they reflect off building elements. The sound of a TV, people talking or a dog barking are examples of airborne noise.
The distinction between these two is especially relevant when it comes to choosing how best to tackle a specific noise problem.
Acoustic treatment
The Merriam Webster dictionary defines acoustics as the “science that deals with the production, control, transmission, reception and effects of sound”.
For the purposes of our discussion, key to this science is assessing a room’s ability to hold sound energy, otherwise known as reverberation: reverberation occurs when sound bounces off multiple surfaces, creating an echo. Reverberation time therefore refers to the length of time it takes for sound to ‘decay’ or fade.
Acoustic treatments aim to lower reverberation times and influence how sound waves behave, either by absorbing or diffusing them. The former literally soaks up sound, whilst the latter scatters it around using carefully chosen surfaces.
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An effective acoustic treatment programme will incorporate a variety of methods, materials and approaches, taking into account the dynamics of a building and the sound requirements for the area in question.
.webp "Sound insulation | Flotex 53043")
Sound insulation
The final concept we will touch upon here is the practice of sound insulation. Sound insulation is all about containing sound within a space, preventing it from seeping out to where it isn’t wanted.
Sound insulation operates on the basis of absorbing or diffusing sound, or a combination of both. As sound can travel throughout a building from the sides, from above or from below, sound insulation is most commonly implemented in the form of acoustic flooring, walls and ceilings.
Now that we’ve covered the basic acoustics jargon, keep an eye out for parts 2 and 3 of this mini-series on sound, where we’ll be discussing the acoustic issues specific to a handful of sectors, as well as ideas on how to tackle them.