The Decibel Scale; Audio Clips - CAKEWALK SONAR User Manual

Here is what a clipped waveform might look like:
Clipping is not usually desirable and may have unpleasant audible effects. Sudden irregularities in the
waveform of any type can cause clicks, pops, and distortion of the original sound.

The Decibel Scale

In acoustics, the decibel (dB) scale is a scale for measuring the relative loudness of two sounds. For
example, environmental noise is often measured as follows:
L = 20 log (p/p0)
where L is the sound pressure level (in dB), p is the sound pressure amplitude, and p0 is a reference
amplitude of 20 micropascals (less than one billionth of atmospheric pressure). On this scale, a barely
audible sound (p = p0) has a sound pressure level of 0 dB, normal conversation (p = 1,000*p0) is at a
level of around 60 dB, and a jet engine at close range (p = 1,000,000*p0) is at a level of around 120 dB.
Similar decibel scales are used in other branches of science and engineering to measure electrical power
levels and other signal levels, always with respect to some reference level.
In SONAR, decibels are used in several places:
• To indicate volume levels of audio tracks in the Track view and Console view
• To indicate the effects of filters and equalizers
The reference level (0 dB) usually corresponds to the current loudness of the sound. A positive change in
decibels makes the sound louder; a negative change makes the sound quieter.

Audio Clips

If you have read from the beginning of the chapter, you should have a good idea of what is contained in
a SONAR audio clip. An audio clip contains a long series of numbers, or samples, representing the
fluctuating amplitude of a waveform. Audio clips are typically quite large, hundreds of kilobytes to
many megabytes in size. By comparison, a MIDI event takes only a few bytes to store.
The Track view lets you see your audio waveforms in great detail; you can zoom in until you see the
individual samples.
You should also now be aware of some things to watch out for when editing your audio data. First, if you
cut audio clips apart or splice them together, you should do so at zero-crossings in the waveform (places
where the amplitude is zero), in order to avoid sudden changes in amplitude that may cause clicks and
pops. Second, you should beware of clipping. Clipping of the audio waveform can occur if you record a
signal at too high a record level, or if you apply audio processing or effects that increase the waveform
amplitude too much. If you accidentally cause the waveform to clip, you should undo the command and
try again with different parameters.
Clipping can also occur in other situations, for example, if you try to play or mix several loud audio
tracks together, the aggregate signal strength may at times exceed the clipping limit, and the output
signal will be distorted. To correct the problem, you can create a volume envelope to reduce the level in
loud audio clips or reduce the track volume in the Console or Track views.
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