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Old 15th January 2006, 11:50 PM   #1
MCPete is offline MCPete  United States
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Default level of recorded pink noise

For my measuring purposes, I would like to know what the RMS voltage taken at each output jack of my CD player should be when playing a CD recording of pink noise. I don't have a multimeter capable of making that measurement and I'd rather avoid the expense of purchasing such an instrument.

The specs that came with the CD say that the pink noise has been recorded at -14 dB below digital peak for 0 V.U. reference operating level.

Based on how V.U. is defined, I think that I might have the answer, but I would like to hear what others might have to say about it to confirm or disconfirm what I came up with.

There is one other thing about pink noise that I am curious about the correctness of and seem to recall having read somewhere. That is that the distribution of energy or power of pink noise approximates that which nominally would occur in a music recording. Is this correct?

Thanks for any feedback.
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Old 16th January 2006, 09:21 AM   #2
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The actual output of a domestic cd player purely depends on the output stage, it has no reference to the level that the cd/audio was digitised at. The only way is to measure it, either with a DMM or calibrated VU meter.
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Old 16th January 2006, 01:11 PM   #3
jcx is offline jcx  United States
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- or read it off the back of the machine, my sony claims "2.0 Vrms" output
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Old 16th January 2006, 01:22 PM   #4
sreten is offline sreten  United Kingdom
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Default Re: level of recorded pink noise

Quote:
Originally posted by MCPete
For my measuring purposes, I would like to know what the RMS voltage taken at each output jack of my CD player should be when playing a CD recording of pink noise. I don't have a multimeter capable of making that measurement and I'd rather avoid the expense of purchasing such an instrument.

The specs that came with the CD say that the pink noise has been recorded at -14 dB below digital peak for 0 V.U. reference operating level.

Based on how V.U. is defined, I think that I might have the answer, but I would like to hear what others might have to say about it to confirm or disconfirm what I came up with.

There is one other thing about pink noise that I am curious about the correctness of and seem to recall having read somewhere. That is that the distribution of energy or power of pink noise approximates that which nominally would occur in a music recording. Is this correct?

Thanks for any feedback.
Hi,

the test CD should have a 1Khz tone at a reference level
(0dB or -10dB) you can measure with a decent multimeter.

You can then use this reading to calibrate pink noise output.

Pink noise has constant energy per octave, so its much more
like music than white noise, however pink noise does not have
the typical frequency power distribution of music nor does it
have the typical dynamic level distribution of music.

Still a decent system measured with a decent microphone and
averaged over a number of typical listening positions will have
a flat pink noise response up to 4KHz or so, above this it should
exhibit a smooth treble roll-off (due to directivity of the tweeter).

/sreten.
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Old 16th January 2006, 02:35 PM   #5
MCPete is offline MCPete  United States
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Hi Sreten,

Thank you for your response.

The CD does have a 1 KHZ test tone recorded on it. The sheet that came with it states that the pink noise track is "level set using 1KHZ sine wave reference". This is greek to me. Does this mean that the RMS voltage at an output jack of my CD player with the 1 KHZ sine wave track being played is identical to that which occurs playing the track of pink noise?
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Old 16th January 2006, 11:17 PM   #6
MCPete is offline MCPete  United States
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"The actual output of a domestic cd player purely depends on the output stage, it has no reference to the level that the cd/audio was digitised at. The only way is to measure it, either with a DMM or calibrated VU meter."

Also, I agree with what pinkmouse had to say (above). It is very unlikely that all domestic cd players would have the same gain of the output stage of the player and thus impossible to predict what the RMS voltage at an output jack of the player should be.
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Old 17th January 2006, 10:16 AM   #7
sreten is offline sreten  United Kingdom
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Quote:
Originally posted by MCPete

The CD does have a 1 KHZ test tone recorded on it. The sheet that came with it states that the pink noise track is "level set using 1KHZ sine wave reference". This is greek to me. Does this mean that the RMS voltage at an output jack of my CD player with the 1 KHZ sine wave track being played is identical to that which occurs playing the track of pink noise?
Hi,

I not familiar with the peak to mean ratio of pink noise but it
would seem reasonable that -14dB peak value of pink noise
would have an equivalent RMS value to ~ a -20dB sine wave.

So your surmisation could easily be correct, it just depends on how the
1Khz sine wave is referenced, as -14dB could also be simply -14dB RMS.

/sreten.
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