Subject: Re: low frequency noise in sound booth From: =?iso-8859-1?Q?Lars_Bramsl=F8w?= <lab@xxxxxxxx> Date: Mon, 17 Dec 2007 10:06:46 +0100 List-Archive:<http://lists.mcgill.ca/scripts/wa.exe?LIST=AUDITORY>Dear List We've had the exact same calibration problems in our sound booths - mostly caused by a ventilation system that produced very large SPL in the 10-20 Hz region. When using a portable sound level meter, there is often not a selectable high-pass cut-off. However there is often the option to select 'C' weighting which is much flatter than the 'A' weighting - flat from 100 Hz - 3 kHz and thus well suited for speech level calibration. So that has been our solution to the calibration issue. There is a good overview of weighting functions on http://en.wikipedia.org/wiki/A-weighting Regards Lars Lars Bramsløw, Ph.D. Oticon A/S, Audiology Kongebakken 9 DK-2765 Smørum lab@xxxxxxxx +45 39 13 85 42 -----Original Message----- From: AUDITORY - Research in Auditory Perception [mailto:AUDITORY@xxxxxxxx On Behalf Of Stuart Rosen Sent: 15. december 2007 08:56 To: AUDITORY@xxxxxxxx Subject: Re: low frequency noise in sound booth I too have had this problem. In our quiet room in central London, you can in fact, just about hear the tube trains as they pass under our building. But even when it appears to be completely silent, our spectrum analyser shows strong low frequency sound. But A-weighting is not necessarily the best way to deal with this problem and is often inappropriate depending upon what one is trying to measure. Our spectrum analyser has the option of summing the power over a specified frequency range, so I simply restrict the measuring range to something like 50 Hz-10 kHz. Yours - Stuart -- /*------------------------------------------------*/ Stuart Rosen, PhD Professor of Speech and Hearing Science Dept of Phonetics & Linguistics UCL 4 Stephenson Way London NW1 2HE England Directions to Wolfson House (where I am based): http://www.phon.ucl.ac.uk/dept/maps.html Tel: (+ 44 [0]20) 7679 7404 Admin: (+ 44 [0]20) 7679 7401 Fax: (+ 44 [0]20) 7679 5107 Email: stuart@xxxxxxxx Home page: http://www.phon.ucl.ac.uk/home/stuart /*------------------------------------------------*/