Subject: Re: Sound volume control in Matlab From: Mark Huckvale <m.huckvale@xxxxxxxx> Date: Wed, 13 Aug 2008 14:34:26 +0100 List-Archive:<http://lists.mcgill.ca/scripts/wa.exe?LIST=AUDITORY>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! Mark Huckvale 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 > much. > > 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 > purposes. > > Best regards, > > > Bob Masta > > D A Q A R T A > Data AcQuisition And Real-Time Analysis > www.daqarta.com > 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 www.langsci.ucl.ac.uk