[PD] sound and current

matthew jones m.jones at signal.QinetiQ.com
Tue Sep 28 10:56:33 CEST 2004

Hi daniel,

a "filter that cuts out DC" is just a filter that removes zero Hertz, since
an offset in the waveform - called here a "DC offset" - can be viewed as a
sine wave that has a frequency of ZERO.  Hence its value never changes.

Since zero Hz is basically a LOW frequency (the lowest physical frequency
you can deal with), high pass filters are often used to remove such nasty
offsets, so that they remove anything below, say, 5 Hz.
Offsets in waveforms are clearly undesirable, since although you can't hear
them (no speakers would be able to reproduce anything this low: the sound of
atmospheric pressure changes is not exactly perceivable anyway...) they can
make your soundcard outputs clip even when the output signals appear
relatively quiet.

Anyway, voltages are used to represent sound once it has been converted to
an electrical signal using a microphone (or whatever).  So the two are
inextricably linked....


----- Original Message ----- 
From: "daniel" <odiv52000 at mailup.net>
To: "pdList" <pd-list at iem.at>
Sent: Monday, September 27, 2004 11:18 PM
Subject: [PD] sound and current

> Hi list.
> In tutorial F01.pulse.pd there is an high pass filter that cuts DC. Does
> it cut that 5Volt off the sound?
> In general im asking for some info about relationship between current
> (DC, AC) and sound, maybe someone could link me.
> best regards
> _______________________________________________
> PD-list at iem.at mailing list
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