Re: Headphones etc

Subject: Re: Headphones etc
From: Alexandra Hettergott (
Date: Mon May 31 1999 - 09:50:09 EDT

-----Original Message-----
From: Daniel Leduc. <leducd@ERE.UMontreal.CA>
To: <>
Date: Monday, May 31, 1999 6:21 AM
Subject: Re: Headphones etc

>>If they are 'open' headphones (foam ear pads), external sounds come in
>>relatively unattenuated. If the student doing the project would like to
>>have a dynamic range of (say) 50 dB, if the ambient sound level in the
>>lab is 55 dB (machines, movement, talking), then there wil be peak levels
>>of 105 dB. While a minor hazard if it is occasional, under Canadian labor
>>standards, exposure to about 3 minutes per day of 95 dB, is considered a
>>safety hazard, and ear protection is required.
>Kevin... 50 dB + 50 dB font 53 dB et non 100 dB.
>N'est-ce pas?

-- about 56dB for 50 + 55dB ; yet this applies to (homogeneous) tones of same
frequency only ; for different tones yet falling within one critical bandwidth it
should be about 98.7dB, and for a multi-tone stimulus exceeding the width of one
critical band about 100.6dB -- in both cases, however, neglecting the interaction of
level and frequency within the auditory area! -- for then it is not the sum of the
single intensities but of their loudnesses. Not to mention masking effects... etc.
etc. etc.
Alexandra Hettergott.
[sources, e.g., Juan G. Roederer, Introduction to the Physics and Psychophysics of
Music (Springer, several eds), which I consider one of the best ones].

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