Software questions MiniMens

[William R. Brohinsky]

Depending on the measurement made and the reference used, the equation 
is either 10(log(measurement/reference)) or 
20(log(measurement'/reference')). The latter case (marked with prime 
marks) is for where reference' and measurement' are squared quantities 
(done to eliminate negative instantaneous excursions, and make a 
quantity that is not tied to time); the former for simple instantaneous 
sound pressure. Look in Benade (whose work I haven't looked at myself in 
decades) and see if he even states what reference he is using. If his 
'loudness' is referenced to Pascals or N/m^2, then the equation to use 
should be 10(log(pressure/ref)), so 6dB will be doubling. If he is using 
Pascals^2, then doubling will be 3dB. In light (where I worked for one 
of the intervening decades), the terms are irradiance and magnitude, 
irradiance being the amplitude of light, and magnitude being the square 
of the irradiance, ie the power in the light. For irradiance, 6dB 
doubles, for power, 3dB doubles. Why? Because of the square function 
applied to derive power.

In sound, especially in 'pro sound', loudness is equated with the volume 
of sound, which is a power measurement. If Benade is dealing 
specifically in amplitude of sound rather than power, his loudness means 
an entirely different thing altogether: hence my remark about sound 
pressure and power being more useful terms than loudness (which means 
everything from the knob setting on the amp to the special change in 
filter characteristics to adjust for the fletcher munson curve to actual 
power.) Magnitude is also a very heavilly over-used word, which I tend 
to try to avoid when talking actual values.

As for the math, I don't want to tell you how many times I've messed up 
addition while guessing right at second derivitives (which I can't do on 
paper to save my life!)

raybro



Robin Hufford wrote:

>Hello William,
>     I don't know where I came up with 3 plus 3 plus 3 then plus 1.5 is
>required to get 10.  A mystery to me, except that the post was done in a
>hurry.
>     So what are you saying?  Benande takes the position as does Bernhard
>that 6db is a doubling of loudness.  Perhaps this is corrected for
>perception.   What is it?
>Regards, Robin Hufford
>
>  
>