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Re: Sound volume control in Matlab
It is also worth noting that Vista (or at least some audio drivers in
Vista) have an output AGC option, which you will probably want to
disable through the control panel.
I found this out the hard way - I was demonstrating in a class how
changes in dB level affects loudness and all my samples came out the same!
Bob Masta wrote:
On 11 Aug 2008 at 18:18, Stuart Rosen wrote:
Has anyone tried to control sound volumes in Vista
through Matlab? There are extra complications over XP in
that each application window seems to have its own
volume setting (which is a good thing) but that seems to
be limited to an overarching volume control that applies
to all windows.
Be very careful with volume controls in XP or Vista.
Windows uses the "kernel mixer" to manipulate the digital
stream so multiple applications can use the same device. It
basically intercepts the data and scales it down before
sending it to the D/A. The D/A thus gets the sum of all
the active streams. The danger is that this is all done
"behind your back"... an individual application does not
know that its volume range has been shortened, or by how
In principle you could just make sure that all other apps
are fully closed before you start your desired app, but
sometimes it's not clear if an app is really gone or just
lurking in the background (and eating up volume range).
One way to avoid this is to get a separate sound card that
is used *only* for your experimental setup.
My understanding is that software that uses ASIO drivers
avoids the problem, by bypassing the kernel mixer. I have
also heard that "kernel streaming" can be used for similar
D A Q A R T A
Data AcQuisition And Real-Time Analysis
Scope, Spectrum, Spectrogram, Signal Generator
Science with your sound card!
Mark Huckvale, Director MSc Speech and Hearing Science
Speech, Hearing and Phonetic Sciences, University College London