Re: Another Ear Question...

In article <s%GOk.11263$_Y1.10862@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx>, "Paul Stamler" <pstamlerhell@xxxxxxxxx> wrote:
"Scott Dorsey" <kludge@xxxxxxxxx> wrote in message
news:gefcip$32j$1@xxxxxxxxxxxxxxxxxxx
Hueyduck <hueyduck@xxxxxxxxxxxxx> wrote:

Also, a doctor once told me that the unit "dB" used to measure losses of
hearings is not the same as the "dB" on a mixer scale.

dB is a not a unit. It is a ratio.

As I don't know much about physics, I had to believe him, since 20dB
seems to be an awfull lot to me (that would mean that I hear some
frequencies 4 times less loud than they should appear to me).

20 dB is a factor of 100.

That is, 20 dB SPL is 100 times the reference sound pressure level,
-20 dBFS is 1/100th of full digital scale, 20 dBV is 100 volts, and
20 dBoz is 6.25 pounds.

But it ain't. At least not for some of those items. +20dBV is 10V, not
100V. -20dBFS will give you a voltage 1/10 that of 0dBFS.

dB is a ratio, and it must be used in conjunction with a unit to be
useful unless you are using it to describe a ratio. For example, you
can say "This amplifier has 20 dB of voltage gain" meaning that what
comes out is 100 times what went in. Otherwise you HAVE to add the unit.

10x, if it's voltage gain.

Without opening the whole can of worms between prescriptivists and
descriptivists, there are two systems in use these days which use dB. One
refers to power, describing the ratio between two power ratios, where dB =
10 x log (P1/P2). The other refers to voltage, describing the ratio between
two voltages, where dB = 20 * log (V1/V2). The first system has deeper
historical roots, and more official sanction; the second system is used, de
facto, far more in audio engineering.

Frankly, I think it's time the standards committees recognized the messiness
and introduced some terminology that would regularize it. Because these days
almost everything we do in the studio has to do with voltages rather than
powers.

The nice part is that when you turn something down 3dB in either system, it
goes down about 3dB in your ears.

Peace,
Paul


Everytime I get into dB I pull out my Electronics pocket Handbook, with all
the voltage and power levels. I agree voltage is a much more relevant term when
talking about levels. I don't quiet follow the 3dB in the ears statement.

greg
.

Relevant Pages

  • Re: Another Ear Question...
    ... useful unless you are using it to describe a ratio. ... refers to power, describing the ratio between two power ratios, where dB = ... The other refers to voltage, ... the voltage and power levels. ...
    (rec.audio.pro)
  • Re: More cable talk
    ... in the power equation for decible 10*log. ... ratio just was the decibel is a ratio. ... I don't think db is a measure of voltage. ...
    (alt.guitar.bass)
  • Re: Antenna question
    ... in voltage and 6 dB is a doubling of voltage. ... that you are reading, as a gain, etc. ... gain or a power gain?- Hide quoted text - ... a power ratio, with a decimal shift. ...
    (sci.electronics.basics)
  • Re: Nepers and Bels
    ... it is meaningless to give a voltage gain in dB. ... to express power ratios, and if the starting point to calculate a power ... are squared to get that power ratio, ...
    (uk.radio.amateur)
  • Re: model ignitions (was Re: DIY vacuum-pump? (for vacuum impregnating))
    ... some wire and a tube over it. ... resistance of the high voltage winding is unimportant ... maximum voltage in a given volume it should be wound with the ... turns ratio on a 12v car coil is about 60:1. ...
    (uk.rec.models.engineering)