Re: [Phys-L] decibels

[brian whatcott <betwys1@sbcglobal.net>]

On 4/29/2019 6:20 PM, Anthony Lapinski wrote:
> A student sent me this short article about the world's quietest room:
>
> www.smithsonianmag.com/smart-news/earths-quietest-place-will-drive-you-crazy-in-45-minutes-180948160/
>
> Anyone ever been in a room like this?
>
> And what do negative decibels mean? The "threshhold of hearing" (10^-12 W/m2)
> corresponds to 0 dB. So a sound quieter than this (say, - 20 dB) has an
> even lower intensity (10^-14 W/m2)? Is there a lower limit?
>
> How does this work with volume control knobs on stereo systems?
Is there a lower limit to sound intensity? Yes! 0 watts/meter^2
Can this be expressed in dB??????? No.?? 10*log(0/10^-12) is undefined.
An approach would be -inf dBA

Brian W