The Logic Off Topic list

At 05:59 AM 20/11/01 +0000, Maak Bow  wrote:

quoting me:
>> 6 dB is twice as loud. Two violins are 3dB louder than one violin, 
>>it takes four to be twice as loud or 6 dB louder.

Replying to me:
>6dBm [or i think dBV] is twice as much SIGNAL
>but twice as loud to the ear [accoustically] is 10dB spl
>
>though of course the dB is not a fixed amount.
>Noticable relative changes in level vary depending on the actual 
>loudness and frequency. Actual loudness should be measured in phons 
>and sones.

Hi Maak ,

I fished out the old textbooks to look this up -- getting rusty I guess.

You are quite correct that a change of 1 bel or 10 dB is "twice as loud" in
terms of our perception. My mistake.

A 3dB change is a doubling or halving of power . eg If you switch off one
channel of a stereo system playing a mono signal the volume drop is 3dB.

A doubling in signal voltage is a 6 dB change -- that's where I got confused.

Regards,
Murray