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....

Matt

-=-=-=-=-=-=-=-=-=-=-=-=- http://www.loopit.org/ -=-=-=-=-=-=-=-=-=-=-=-=- ----- Original Message ----- From: "daniel" odiv52000@mailup.net To: "pdList" pd-list@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

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