[linux-audio-user] Quiet PC Components?

[Dan Mills]

On 26 Feb 2006, at 22:49, Kevin Cosgrove wrote:

>
> On 26 February 2006 at 20:50, Dan Mills  
> <dmills at spamblock.demon.co.uk> wrote:
>
>> Surely -INF dB SPL?
>
> Negative dB would imply that the unit absorbs sound.  Do you think it
> does that?  0dB indicates it neither creates nor absorbs sound.


Err No!

0dB indicates a signal having the same power as the reference (in  
this case 0dB indicates a signal  having an amplitude of 20uPa). Note  
that referencing a scale based on power to a pressure level is a  
little unnatural, but as long as the base pressure and viscosity are  
constant it can be done.

No power is -infinity in any dB scale by definition, and Negative dB  
levels are routinely encountered, for example a transmitter may be  
specified as having an output of 20dBm, or -10dbW, these two  are  
equivalent it is just that one is referenced to 1mW, the other to 1W.

Regards, Dan.