Re: measuring output volume from headphones

[Frank Russo <russo@xxxxxxxxxx>]

You need a dummy head or a coupler to do this properly. The coupler sits
between the headphones and a SLM (like the one you are using from Radio
Shack). 

Professional couplers are generally available for super-aural headphones
such as those used in audiometry (good option but expensive for a single
use). Here are some other options to consider:

You can try using a "semi-professional" coupler that can be set up for
use with various types of headphones -- e.g.,
http://www.digital-recordings.com/coupler/coupler.html (inexpensive
option that may be acceptable for situations where precision is not
critical)

You can try building a coupler yourself by fitting the base of a
cone-shaped cylinder (e.g., a strofoam coffee cup) with a rubber seal
(bad option that should only be used for rough equalization -- not for
absolute measurements!)

You can equate the two systems perceptually. Have a small subset of
listeners scale loudness for a few levels of output on each machine.
Adjust sound output level on each respective machine so that sound
output at test is of equal loudness (good option but this won't provide
you with dB SPL levels that can later be reported)

Finally, you can find someone local that has a dummy head (complete with
pinnae and ear canal embedded microphones) and ask to borrow it for a
day (best option).

 
------------------------------------------------------------------------
-
Frank A. Russo, Ph. D.
 
Assistant Professor
Department of Psychology
Ryerson University
350 Victoria Street
Toronto, ON
M5B 2K3
Canada
 
Email: russo@xxxxxxxxxx
Web: http://www.psych.ryerson.ca/russo
Tel: 416-979-5000 ext. 2647
Fax: 416-979-5273

-----Original Message-----
From: AUDITORY Research in Auditory Perception
[mailto:AUDITORY@xxxxxxxxxxxxxxx] On Behalf Of Robbin Miranda
Sent: Wednesday, September 06, 2006 3:11 PM
To: AUDITORY@xxxxxxxxxxxxxxx
Subject: measuring output volume from headphones

Hello,
Can any of you recommend a way to measure the output volume/decibel
level from headphones?  We will be testing participants using auditory
music and speech stimuli on two different computers (depending on
availability of the two testing rooms) and would like to make sure that
the output volume level is equivalent at both locations.  We do have a
decibel meter (from Radio Shack), but this doesn't seem feasible to use
with headphones.

Thanks,
Robbin

Robbin Miranda
Interdisciplinary Program in Neuroscience
Georgetown University
3900 Reservoir Rd., NW
Washington DC 20007
(202) 687-8449