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/* Recording a sound */ numbers :P
A sound is recorded by making a measurement of the amplitude of the sound at regular intervals which are defined by the ''sampling rate'' and to a vertical resolution (between the lowest and highest points on the wave) that is called the ''bit-depth''. The act of taking the measurement is often called ''sampling'' and each measurement unit is called a ''sample''. A file which contains samples is often called a waveform, sound sample, audio sample, ''etc.''
The sampling rate defines the rate/frequency at which the measurements are taken. The higher the sampling rate, the faster/more frequently the measurements are taken, and the higher the maximal frequency that can be represented by the signal. Conversely, the lower the sampling rate, the slower the measurements are taken, and the maximal frequency that can be stored is lower. The sample rate is described by the "Hz" unit of measurement. The "Hz" unit of measurement means "per second". Therefore, a sampling rate of 44010 44100 Hz , a.k.a. 44.1 kHz, means 44010 that 44100 measurements are taken each second (in other words, one measurement every 1/44010 44100 th of a second).
If the sampling is too low, then changes in the sound which occur between each measurement will not be measured. Because higher audio frequencies are defined by oscillating more rapidly, this means that lower sampling rates can store only lower frequencies. Therefore, the faster the measurements are taken, the more accurate the recording will be, and thus the higher the quality of sound that can be recorded. Of course, at high sample rates, because there are many more measurements taken, the resulting size of the file (containing the audio data) can be large.
[[Image:wave7.gif]]
''Fig 7. An amplitude/time graph showing the sampled waveform. As explained in the note for Figure 4, this is only a visual representation of the digitally stored audio, '''not''' of the signal that would be output by any competent audio card. However, it does illustrate how low sampling rates reduce the bandwidth of frequencies: This waveform was generated at a low sample rate, and therefore the resulting waveform is much more coarse compared to Fig 4. Notice that although the general shape is similar to the original waveform, much of the smoothness is is lost between the time of each measurement. The loss of smoothness also means loss of information: the lower the sample ratingsampling rate, the more information is lost; in other words, the maximal frequencies frequency that the signal can represent is lower. Similarly, lower bit-depths mean that the signal is less accurate, and in extreme cases can generate audible noise, . Therefore, to record a sound, it is best to use relatively high sampling rate and bit-depth; CD audio's 44.1 kHz and 16 bits should be more than adequate for most uses, especially storage of CPC cassettes.''
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