It
is a fundamental principle in acoustic analysis that any waveform, however
complex it might be, can be broken down into simple waveforms of different
frequencies. The operation of doing this is called spectral analysis,
and
in some ways is rather like breaking down white light into the rainbow
pattern of colours that make up its spectrum. In carrying out the acoustic
analysis of speech sounds, we can discover much more by looking at the
result of a spectral analysis than by looking at the original waveform
that was captured by the microphone. This picture shows the result of the
spectral analysis of the word ‘see’ that we have already looked at. This
type of picture is called a spectrogram. At one time there
was a fashion for calling such pictures "voice-prints", but this led to
some very dubious claims being made about identifying people by their voices
for legal purposes, and the name is not now used except (sometimes) by
gullible journalists.
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