Understand Methods and Principles of Sound Design and Production

Sound File Formats

An audio file format is a file format that stores digital audio data on a computer system. It can be either uncompressed or compressed to reduce the file size. There are many uncompressed formats, such as Pulse-Code modulation (PCM) which is stored in .wav (it is based on the Resource Interchangeable File Format [RIFF]) file on windows and an .aiff (it is based on the Interchangeable File Format [IFF]) on Mac’s, they are both designed to store any combination of sampling rate or bitrates, which is suitable for original recording. There are many compressed formats, such as MP3 formats and AAC formats, these offer a range of degrees of compression, measured in bit rate, the lower the rate, the smaller the file and the lower the quality of sound.

Lossy compression reduces the size of the original file but results in lost data and quality from the original file; this can usually be found on image files but also on audio files. In audio files the lossyness can be heard by the audio sounding watery and losing its range of the audio.

Lossless compression reduces the file size also, but instead of losing quality or some data of the file, the file’s quality stays the same as it originally was, it rewrites the data of the original file but makes it more efficient. It uses algorithms to encode the data in such a way that it can be restored to it’s original state.  The disadvantage to this is that it requires an additional encoding stage and a specific software available to the user.

Composer Focus

Audio Limitations of Game Platforms

The main audio limitations that have existed previously within games is the size of them, when games were first created they came on 1.44 MB floppy disks, this left very little room for sounds in games. Most games of the 80’s and early 90’s used 8Bit sound; this made the sound seem very robotic. Towards the end of the 90’s, following the invention of the Compact Disk (CD) and the MP3 and OGG files being used more and more, games started using what was considered as “real” music. Real instruments could finally be used within games and sound effects were becoming more and more realistic and better, whereas in older games the sound effects were just sounds of beeps. Sound banks are used more and have grown over the years too, years ago the developer of the games had to go out and record a certain sound to use in games, this proved quite costly but now there are sound banks where the sounds are already created and offered to the developer for free. Sound in games now is not limited.

Audio Recording Systems

At the heart of a hard-disk recording and editing is digital audio. When we digitally record things, sound is converted into an electrical signal by a microphone, the signal is then coded into numbers by an analog to digital converter (ADC). The numbers are then stored in memory and when played back upon demand it sends the numbers to a digital to analog converter (DAC). This resulting signal is sent through an amplifier and speakers where we hear the reproduction of the original sound. Analogue recording methods store signals as a continual wave. With digital recording, audio and video is directly recorded to a storage device as a stream of integers, representing the change in sound. The MiniDisc is a data storage device used to record 74 – 80 minutes of digital audio or 1GB of Hi-MD data. CD’s are an optical disk used to store digital data, originally it was developed to store and play sound recordings. Digital audiotapes (DAT) are signal and playback mediums designed by Sony, it has the ability to record at higher, equal or lower sampling rates than a CD. A digital audio workstation is an electronic system designed to record, edit and playing back digital audio. Multi-track recording is a method of sound recording that allows for separate recordings of multiple sound sources..

Audio Sampling

The sampling rate of audio must be double the frequency recorded. CD audio is sampled at 44.1 KHz, (which means the wave is measured 44,100 times per wave) the frequency of CD audio would be about 22.05 KHz. If you compare the bit depth of an image and audio it’s very much the same, there are 3 common bit depths 8 bit, 16 bit and 24 bit. 8 bit images have 256 colours available to be seen, making images look quite strange; it’s the same with audio if the audio is 8 bit then the audio would sound grainy and not very clear. 16 bit images have 65,536 colours available to be seen and again that’s the same with audio, 16 bit audio is most commonly used for CD’s and DVD’s. 24 bit has the ability to show 16.7 million colours in an image and that’s the same with audio, only blu-ray discs support 24 bit audio. With the bit depth you have to multiply it by the sampling rate and you get the quality potential for the audio.