#14: Acoustics 

Acoustics, the qualities, characteristics and physics of sound within a envrionment. This is the foundation principle of what I am looking to do with this project. Acoustics is a extremely complex area of study, and can not entirely be covered by me alone. However some of the core elements are fairly easy to grasp and make for a great starting point for a virtual audio experience. 

 

The video game project will essentially be a digital simulation of some basic acoustics, therfore at least a simple understanding of the basics is required to move forward with this digital simulation. 

Reverberation & Rt60 

Reverberation (reverb) is a name given to a characteristic of sound when it interacts with a reflective surface. This is most commonly heard when inside a large room like a church or cathedreal... Or, open spaces with reflective surfaces such as a quarry, cave or cavern. 

 

These reflections can be thought of as the sound 'bouncing' from wall to wall and eventually heading to the listener. The dimentions of the environment will determine the kind of reverb effect that the listener hears. This is usually measured by what is known as an RT60. RT stands for Reverb Time with the 60 refering to 60dB.

 

Acoutics Reverb reverberation reflections - Mootzart

Absorption coefficients 

 

This is a term which represents a value given to a material based on its ability to absorb energy from a sound waveform. A extremely dense material will likely be more reflective then a softer material which has a structure enableing sound to penetrate it.

 

The values given are usually measured in a value between 0 and 1. With 0 representing no absorption and 1 being equal to total absorption [21W]. These values are used when designing new acoustic environments or planning for adapting envrionments to make them more suitable acoustically. This part of acoustics will be a great help when attempting to create a digital acoustic environment as it gives us some pre determined values that can be potentially coded into a working script within Unity. 

A Brief overview 

Doppler Effect 

 

The Doppler effect is somehting that I will likely not implement to a great amount in the final porject. However it is a important element that I believe will be used alot within the future of spatial audio within video games. 

 

The doppler effect is a phenomenon that is usually only heard when a sound source (sound wave) is moving in relation to the listener. The effect causes the sound to manipulate as if it is changing in pitch. This is due to the size of the waveform and its frequency content. A police siren is a good example of when we most commonly experience this effect. As the police car moves towards the static listener, the shorter (high frequency) waveforms get to the listener first. As the vehicle moves past the listener the longer wavelengths take over as the higher frequencies lose energy. This sounds as if the pitch of the sound is changing from high to low.

 

 

 

Mootzart.

 

A RT60 measurment is a way of measuring how long it takes for a sound sources peak level of amplitude to decay by 60dB. This time will determine the environments RT60. This is a very important thing to note when working within a environment as it plays a heavy role when colouring the sound. Reverb is not always desired on recordings for example as it adds room/space to the sound which may not be wanted for say a clean Jazz recording. 

 

There are plenty of places online that show you how to obtain a RT60 such as the video below... [12DL]