Windows Multimedia functions: waveOutReset & waveOutPause

[Neill]

While playing an audio buffer, I noticed the call to
waveOutPause/waveOutReset will cause an audible click. I solved this by
turning the volume down before calling these functions. Is there a more
elegant solution?

Best Regards,
Neill

[Bob Masta]

There will be an unavoidable click whenever you
stop (or start) a waveform suddenly, especially at
a high-level peak. The only solution is to change
the level more slowly, typically over (say) 100
msec or more. (You can get away with faster
changes if the waveform frequency is higher, so
the change takes place over one or more waveform
cycles.)

This is related to the spectrum of the truncated
wave. A vertical edge (rising or falling)
represents a lot of high frequency energy, which
is perceived as a click. You can best visualize
this with a spectrogram, which shows time on the
horizontal, frequency on the vertical, and energy
(loudness) as color or density.

You may want to check out my Daqarta software,
which shows spectrograms, spectra, waveforms, etc.
Examples of spectrograms:
<http://www.daqarta.com/dw_sgram.htm>

You can use the Daqarta signal generator to create
tone bursts with various frequencies and rise and
fall times, and listen while watching the
spectrogram. You can set the bursts to start at
random phases of the tone frequency, or to always
start at the same (adjustable) phase to get the
maximum click effect.

You will see on the spectrogram that there is a
vertical spike across many frequencies when you
hear an audible click. As the rise/fall times
increase, the spike becomes fainter and the click
less audible.

Daqarta is $29 to buy, but you don't need to buy
it for the above experiments. Even after the 30
day / 30 session trial expires, the signal
generator keeps working. You won't be able to
view external input signals, but you can still see
and hear the generator output.

Please let me know if there are any questions,
either here or on the site's Contact page.

Best regards,

Bob Masta

DAQARTA v4.51
Data AcQuisition And Real-Time Analysis
www.daqarta.com
Scope, Spectrum, Spectrogram, Sound Level Meter
FREE Signal Generator
Science with your sound card!