Re: [AUDITORY] how often should we calibrate? ("Ward R. Drennan" )

Subject: Re: [AUDITORY] how often should we calibrate?
From:    "Ward R. Drennan"  <drennan@xxxxxxxx>
Date:    Mon, 7 Jan 2008 22:56:53 -0800

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@xxxxxxxx> 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 >> >> >> > > -- > 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@xxxxxxxx > 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

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