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Old 01-31-2010, 01:41 PM
Nate Bargmann
 
Default Decibel value mentioned to tones (siggen package) not working as expected

* On 2010 31 Jan 08:03 -0600, Foss User wrote:
> On Sun, Jan 31, 2010 at 7:22 PM, Jan Piet Joris en Corneel
> <jpjorisencorneel@gmail.com> wrote:
> > A difference of 2 dB cannot be noted by most people. *The minimal
> > difference you can hear is 3 dB, but please try some more difference
> > e.g. 10 dB.
>
> I tied -8 dB and -20 dB this time but both the sounds still sound the same.
>
> Command:
>
> rm notes.wav; tones -w notes.wav 1000 440@-8 0 440@-20 && play notes.wav

It's quite possible that your levels are still too "hot". Open the
file in Audacity and be sure the waveform isn't "clipped". You should
be able to see nice rounded peaks and valleys in the sine wave. If any
part of the waveform is flat or jagged, reduce the level further.

Keep in mind that average voice levels on a telephone line are around
-16 dBm. That is 16 dB lower than 0 dBm (1 milliwatt) or 0.025 mW.
Not a lot of power.

Now, you are using dB in this message. You may be well aware that dB
is a ratio and not a unit of measure. To have any meaning the dB is
suffixed with a unit of measure to indicate the ratio to the reference
level or it must be assumed to be a ratio. Common values are dBm
(reference 1 milliwatt), dBW (reference to 1 Watt), and many more:

http://en.wikipedia.org/wiki/Decibel

Note also that 0 dBm is not 0 milliwatts!

HTH,

- Nate >>

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