On Tue, 24 Jan 2012 17:33:29 +0100, Mxsmanic wrote:
Someone here said something about trombones not producing symmetrical
waveforms, which reminded me of these anomalies. How or why would a
particular instrument produce a waveform that isn't symmetrical around
zero?
To add to the good answers already given, it might be worth pointing out
that a wave form that is asymmetric doesn't necessarily have a DC offset.
A high-pass filtered regular wave of short positive going pulses will
have equal area under the short but tall positive pulses and the longer
but lower amplitude negative-going part of the waveform.
So the *average* is zero (no DC offset), but the positive *peaks* are
bigger in amplitude than the negative peaks.
As for the mechamism of production: brass intrument tone is produced by
the player's lips opening and closing rapidly and interrupting a flow of
air. The waveform is asymmetic because the closed and open times are very
different (I'm not sure which way round).
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Anahata
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