Digital Audio is a set of numbers representing the sound. Capturing digital audio involves taking an existing sound and sampling it. The input audio source can either be from a microphone, musical instrument, television or cassette recorder. Regardless of source, the analogue input is converted by the analogue to digital converter to give the digital audio. Two factors will determine the quality of digital audio, Sampling Frequency and Audio Resolution. Sampling Frequency Analogue values are converted to digital values by the process of sampling. Sampling involves the computer sampling the sound thousands of times a second. The number of times a second (frequency) that a sound is sampled is known as the sampling frequency. Common sampling frequencies are 44 KHz (kilohertz), 22 KHz and 11 KHz. (This means the sound is sampled 44,000 times per second). The diagram below shows how the original audio source was sampled at two different frequencies, 44 KHz and 22 KHz. Note how much nearer the original sound the 44 KHz sampling is.
The higher the sampling frequency, the better quality the digital sound will be, but the more memory that will be used. Recording in stereo will take twice the amount of memory as you are recording two channels instead of one. The table below shows the memory taken for 1 minute of audio at different sampling frequencies.
Answer the following questions in your jotter. 1. What would be the storage requirements be for the following conditions:
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