Re: measuring output volume from headphones -- follow-up

[Bob Masta <audio@xxxxxxxxxxx>]

You may be interested in my DaqGen freeware at
   www.daqarta.com
This is signal generator software that allows creation
of very complex stimuli, including several different
basic waveforms (plus arbitrary) and different noise
generators including band-limited.  Sources can be
modulated with various modulators, and a modulated
stream can be used as the modulator for another stream.
You can create up to 4 independent streams per channel.

Regarding your particular needs for volume control, DaqGen
allows numeric entry of Wave and Master volume step numbers.
(And you can save these settings with a stimulus setup.)

Note that Windows only deals in volume "steps".  There is no
way via software to determine the size in dB of any given step,
and in fact many sound cards have extra "dummy" steps
where the attenuation doesn't change at all from the prior step.
(This is apparently to fool the user into thinking the card has
finer control than it really has.)  Also note that the dB size of 
the actual effective steps is not constant over the range...
typically the resolution is finer at higher levels.

DaqGen includes facilities to allow you to calibrate the
steps on your sound card in dB, after which you can set dB
directly and it will skip dummy steps and find the best
combination of Wave and Master settings to hit your target
value.  If you wish, it can also adjust the raw generated level
as needed to "fill in the cracks" between attenuator settings
to give extremely fine total resolution (fractional dB).

DaqGen is the stimulus generator portion of the upcoming
Daqarta for Windows, which I hope to release in a month or so.
Daqarta can perform the attenuator calibration automatically,
by adjusting input and output steps while measuring the response
to a generated test tone via a loopback cable.

I would be glad to answer any questions about either program.


Best regards,

Bob Masta





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On 7 Sep 2006 at 11:50, Robbin Miranda wrote:

> Thank you to those of you who responded to my previous question.  Your comments were extremely helpful!  Using a dummy head or coupler seems like a feasible option for the initial set-up of our two testing locations (we will be using the same type of headphones at each location).  However, I would also like to be able to quickly check the volume just prior to testing each participant (in case another user adjusts the computer's volume settings).  On my computer (Windows XP), all I have been able to find, even 
in the advanced settings, are scrollbars indicating the volume level.  Is there any way to check/adjust numerical values of the volume setting?
> 
> Thanks again,
> Robbin
> 
> Robbin Miranda
> Interdisciplinary Program in Neuroscience
> Georgetown University
> 3900 Reservoir Rd., NW
> Washington DC 20007
> (202) 687-8449
> 
>