Understanding Building Acoustics Design - Sound Waves

Most people spend quite a hefty sum of money trying to alter their existing spaces to make them acoustically bearable. Building a soundproof room at the initial stages of construction is way more cost-effective and efficient when compared to altering a room to soundproof it after it has been built.

It is always important to design a comfortable and sound space. And a good building design will amount to nothing if the user experience is a horrible one.

In order to understand how to solve potential acoustic problems, it is important to understand the basic principles that affect the sound and its behaviour in any space. Acoustic materials are then checked for their acoustic rating and implemented in the building design.

The behaviour of Sound Waves

Reflection off of the surface
Diffraction around the surface
Transmission into the surface or new medium

1. Reflection

When sound waves are reflected, it can lead to one of the following:

An Echo - this is when a sound is reflected back to the listener after hitting a surface or medium.
A Reverberation - this is when a sound persists even after its source has stopped beforehand.

Both of these factors are known to adversely affect the acoustics of a space. Sound Absorbers are often used in such circumstances to avoid them.

- Some common sound-absorbing materials include:

Heavy curtains
Fibreboards or fibreglass insulation
Acoustic foam or panels

Natural Materials that have the ability to absorb sound are:

Pure Cotton Fibres
Bamboo
Coconut husk
Medium Density Fibreboard (MDF)

2. Diffraction

The change in the direction of the sound waves when it passes over an edge of a surface is known as diffraction.

Diffraction depends on the ratio of the wavelength of the sound to the size of the obstacle, i.e., the longer the wavelength, the stronger the sound diffraction.

Diffraction can also pass through openings. In this case, the smaller the opening, the larger the percentage of sound that passes through the opening.

- Ways to provide good soundproofing to avoid diffraction are:

Proper sealing of the room to avoid any openings
Build tall fences to reduce the effect of diffraction at highly disturbing neighbourhoods
Build solid walls so that they reflect some sound waves and absorb some, resulting in very little diffraction of sound.
Placing objects or plants on top of walls, such as shrubs, can help absorb some of the sounds that might get diffracted at the top. Dense vegetation is an excellent way to absorb sound and prevent diffraction.

3. Transmission

Transmission is the propagation of sound waves through a surface or medium. Sound waves are transmitted as both longitudinal waves and transverse waves through a solid medium.

Regardless, sound transmission happens through gas, liquid and solid. Although in the built environment, some amount of sound tends to pass through hard surfaces such as glass, tiles, hardwood, etc.

- Ways to Reduce Sound Transmission in a Building

Reduction of sound transmission between units can be done by providing a partition between each unit.
The sound reduction can be done by sealing holes and gaps so that sound doesn’t escape a certain space.
Soundproofing wallpapers, curtains or blankets can be preferred in spaces that require high amounts of sound reduction.
You can float the floors by laying insulation between the joists of the floor so that creaks can be prevented. It also primarily prevents the travel of noise between different levels of the building.
Insulate the interior walls to break the path of sound from travelling between different spaces. This also helps stop sound vibration and absorb the excess sound.

It is never too early to start worrying about the noise from the crying baby next door, or the honking drivers on the adjacent street. Because acoustic consideration is as important as the building design itself.

Architects hence have the responsibility to understand and implement the right building acoustic methods during the initial stages of the design process.