Re: Low frequency sound from PC (Matt Flax )

Subject: Re: Low frequency sound from PC
From:    Matt Flax  <flatmax(at)IEEE.ORG>
Date:    Fri, 4 Oct 2002 12:17:14 +1000

Hmmm this is an interesting one ! Most consumerables with pre-amp outputs (such as sound cards) have what are called coupling capacitors at their outputs ... these capacitors are designed to stop DC (0 Hz) signals from leaking between systems. Now these coupling capacitors will probably also affect the 5Hz signals. Now this may not be the case for sound cards - but I think it might be ... perhaps someone else you know knows ? In order to overcome this you can either build your own bits ... try amplitude modulating your signal up in frequency to say 100 Hz. Spit that out the computer sound card... Then build a filter which removes the modulation ... a demodulation circuit for example. Using that technique you can use your regular computer with modulated signals and a demodulator/pre-amp. Another idea might be to create beats using 2 signals which are close to each other in frequency. This option would require careful design and probably require an custom analog mixer (with no coupling capacitors). for example ... use the left channel (of your sound card) for signal 1 and the right channel for signal 2 ... design the auditory signal so that when added, beating occurs ... low pass filter that and wahlah ... low frequency components restored .... There might be some off the shelf solutions as well ... but they would cost alot more to make, unless your time is expensive ! Perhaps someone has already reported on this in the seismology world of research ... where frequencies tend to be very low. Matt On Thu, Oct 03, 2002 at 06:34:53PM -0700, Jishnu Subedi wrote: > Dear List, > I am looking for suggestions to produce infra and low > frequency sound from 5 Hz and below to 100 Hz. Can I > use PC for this purpose? Does anyone have experience > which sound card, amplifier and loud speaker perform > best in this range? > > Thanks in advance! > > Jishnu > Graduate Student > Saitama University, Japan > > > __________________________________________________ > Do you Yahoo!? > New DSL Internet Access from SBC & Yahoo! > -- WSOLA TimeScale Audio Mod : FFTw C++ : Vector Bass : Multimedia Time Code :

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