Re: Lowering audio volume with Windows XP Pro. SP3's Sound Recorderresult distorted audio quality?

Ant wrote:
> Hello.
>
> Is it me or does lowering my WAV's audio volume result in an updated
> Windows XP Pro. SP3's Sound Recorder? Is this a bug in this program or
> something else?
>
> Also, does anyone know of a good free audio program that will do batches
> to lower audio volume in a bunch of old WAV files? Doing one by one is a
> pain in the butt/abdomen.
>
> Thank you in advance.

What I do for testing recording, is a "what you hear" kind of test.

It's possible for a lot of sound cards, to record what is
currently being played back. The patch panel inside the
chip, has the resources to allow you to do this.

Program #1 (playback) -----------+------> speakers
|
summing
Program #2 (record) <---------junction

You can fire up Audacity, and use it to generate a signal.
Then, leave Audacity in playback mode, sending out, say, a
sine wave.

http://audacity.sourceforge.net/

Now, go to Sound Recorder, and record the signal. Sound
Recorder would be "Program #2" in the diagram.

I think I tried to do both inside Audacity at the same
time, but it won't run full duplex. That's why I needed
two programs, to evaluate the sound hardware.

Later, load the recorded signal from sound recorder, into
Audacity, and compare the two waveforms.

Doing so, can show you various kinds of distortions, crackling,
pops, or the like. And then you can judge the distortion type,
and figure out a remedy. Or, even post a picture of the
recorded waveform, on imageshack.us, for comments.

Another kind of test signal that is handy, is an "impulse".
Using a suitable sound program, you "draw" a waveform, being
careful to not exceed the Nyquist limited bandwidth of the
system. (In other words, you can draw a square wave with
vertical edges, but due to the known bandwidth limitations
of your sound system, the pulse should really be drawn as
some kind of trapezoid. You wouldn't go out of your way,
to draw a signal, which is outside the bandwidth of the
system. Here, my rise and fall times are limited.)

----
/ \
------/ \--------

The purpose of impulse testing, is to spot the addition
of "echo" by the sound driver. My SoundMax AC97 audio chips,
had a 30 millisecond echo/delay added for "concert hall realism".
And, it couldn't be turned off. Even with the sound effects
control panel set to "None", the echo was *still* there. The
usage of the pulse, makes it easier to look 30 milliseconds
downstream, on the recorded waveform, for a tiny copy of the
pulse. It's a subtle form of "digital mutilation", which
causes a busy sound sample to "sound muddy". So if you
"hear mud", then check for an artificial echo that has
been added. The cure in my case, was to switch to a
PCI sound card, and turn the SoundMax off.

HTH,
Paul