Re: Low frequency sound from PC

[Matt Flax <flatmax@xxxxxxxx>]

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!
> http://sbc.yahoo.com

--
http://mffm.darktech.org

WSOLA TimeScale Audio Mod  : http://mffmtimescale.sourceforge.net/
FFTw C++                   : http://mffmfftwrapper.sourceforge.net/
Vector Bass                : http://mffmvectorbass.sourceforge.net/
Multimedia Time Code       : http://mffmtimecode.sourceforge.net/