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Re: [AUDITORY] how often should we calibrate?



A question to consider is how sensitive are your experiments to level changes? Often, a few dB one way or the other isn't going to make a difference in the result. Sometimes it does, depending on the test. How much do your headphones or ear inserts drift day to day?

Audiometers get calibrated once a year (!)


On Mon, 7 Jan 2008, Jeremy Federman wrote:

Hi -

Although I sympathize with your desire not to have to train all your
research assistants to do otoscopy, how do you plan on eliminating middle
and outer ear problems as potential confounds without looking in subjects'
ears?  It would seem to me the benefits of inserts (e.g., disease control,
eliminate risk of ear canal collapse, increased inter-aural attenuation,
etc.) outweigh the training requirements especially considering the risk for
possible contamination of your experimental results.  Your method of using
supra-aural phones for calibration is unclear to me.  Regardless, the two
types of phones you are using likely have different response
characteristics.

Regarding calibration frequency, we typically calibrate prior to the first
test session of each day as an absolute bare minimum.  Frequently, we
calibrate more often depending on the equipment and setup involved.  We have
many people using equipment, so our risk for being out of calibration may be
higher than others.  In any case, if I were you, I would ask myself, "How
much risk am I willing to put up with?"  In other words, would the savings
in time (and cost) spent on calibration be worth losing data if calibration
problems were discovered after test sessions, or, worse, not discovered at
all...

With kind regards,

Jeremy

On 1/7/08 4:31 PM, "Ferguson, Sarah Hargus" <safergus@xxxxxx> wrote:

Hello all - As I said, my recent trouble with booth noise has raised a
larger question for me. With the digital equipment most of us are using
nowadays, how often do we really need to calibrate?

I can't use insert phones for all of the experiments in my lab, mostly
because of the time it would take to teach every lab member how to
perform otoscopy. So my plan for experiments using supra-aural phones is
to measure the maximum output of the system for the supra-aural phones,
use that level to determine the needed attenuator settings, and then use
insert phones to confirm that the attenuator is doing what it's supposed
to do.

Certainly I need to go through these steps at the beginning of an
experiment. But how often should I repeat them? I was taught, way back
when, to calibrate every day that data were being collected. But if the
signal is a digital file stored in the computer, and the signal is being
delivered through digital equipment, is that really necessary?

~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~
Sarah Hargus Ferguson, Ph.D., CCC-A
Assistant Professor
Department of Speech-Language-Hearing: Sciences and Disorders
University of Kansas
Dole Center
1000 Sunnyside Ave., Room 3001
Lawrence, KS  66045
office: (785)864-1116
Speech Acoustics and Perception Lab: (785)864-0610
http://www.ku.edu/~splh/Faculty/FergusonBio.html



-- Jeremy Federman, MS, CCC-A PhD Student & Research Assistant Dam Maddox Hearing Aid Research Lab Department of Hearing & Speech Sciences Vanderbilt University Nashville, TN 37232 Jeremy.federman@xxxxxxxxxxxxxx



Ward R. Drennan, Ph. D.
VM Bloedel Hearing Research Center
Department of Otolaryngology
University of Washington Box 357923
Seattle, WA 98195
Office: (206) 897-1848
Fax: (206) 616-1828