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Re: low frequency noise in sound booth

I have always used dBA to circumvent that problem. It could be anything: furnace, boiler, engine noise, traffic noise from outside propagating inside. It's not easily audible at those frequencies.

This might provide some useful information:
Arlinger (1991). "Normal hearing treshold levels in the low-frequency range determined by an insert earphone," JASA 90, 2411-2414.

Ward R. Drennan, Ph. D.
VM Bloedel Hearing Research Center
University of Washington Box 357923
CHDD Building Room CD176
Seattle, WA 98195-7923
Phone: (206) 897-1848
Fax: (206) 616-1828

Please note the confidentiality of e-mail cannot be guaranteed. If you are concerned about confidentiality of specific information, do not send it by e-mail.

----- Original Message ----- From: "Ferguson, Sarah Hargus" <safergus@xxxxxx>
To: <AUDITORY@xxxxxxxxxxxxxxx>
Sent: Friday, December 14, 2007 1:35 PM
Subject: low frequency noise in sound booth

Hello list - I've run into a very annoying problem in my (double-wall) sound booth. When I try to calibrate, I'm getting floor noise of 75-80 dB SPL WITH the earphone (which isn't connected to anything) on the 6 cc coupler, WITH the door closed. The spectrum analyzer shows a peak around 65-70 dB SPL at 16 Hz, with energy about 20 dB below that at 12 and 20 Hz - and nothing else, really.

I have two questions:

1) Does any one have any ideas about what could be causing this? Three
gentlemen from Facilities Operations worked on this for over an hour
this morning, turning off lights and air handlers and exhaust fans -
they even went out on the roof to turn things off. Nothing that they did
had any impact on the noise.

2) How low can I reasonably expect my floor noise to be? While trying to
pin down the onset of this noise, I realized that I never write down the
level of the floor noise, just the levels of the sounds I'm calibrating
(which have often been at levels much lower than 75 dB SPL). With all
this troubleshooting I've completely lost my bearings about what I
SHOULD be getting.

~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~
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