How loud is 250uV white noise?

81bas · 9th April 2010, 05:07 PM

Hi all!

In the specs for some A/V receiver with AB amplifiers inside is written SNR 110dB and RMS background noise voltage 250uV. How loud is such noise applied to the speakers? Will be this noise audible? From which distance to the speakers?

Thanks!

SpeakerScott · 9th April 2010, 05:19 PM

Quote:

Originally Posted by 81bas

Hi all!

In the specs for some A/V receiver with AB amplifiers inside is written SNR 110dB and RMS background noise voltage 250uV. How loud is such noise applied to the speakers? Will be this noise audible? From which distance to the speakers?

Thanks!

That would be 0.0000000078125 watts into an 8 ohm load. Very quiet. Most amps I've ever owned had an audible hiss when placing your ear very...very...close to the tweeter.

-Scott

WithTarragon · 9th April 2010, 05:19 PM

We do not have enough information yet to guess at this answer.

Your speakers will have a specification that translates voltage (usually 2.83 volts) to a dB SPL output at 1m away (sensitivity or perhaps effciency). This will be in the range of 85 to 105 dB per 2.83 volts.

At 250 uV you will be about 80 dB below this. Whether this is audible or not can not be determined exactly. Please remember these numers should be weighed against the noise floor in the room iteself.

I have not bothered discussing some of the 2nd order effects in this analysis. Others may feel the need to go crazy over htose details.

Good Luck,
-Tom

event horizon · 05:35 PM

If that spec is real i should imagine there would be the deafening sound of silence within an foot of the speaker. After all that kind of noise will put 0.000000007 W RMS into it

Or 7 billionths of a watt

wahab · 9th April 2010, 05:34 PM

Quote:

Originally Posted by 81bas

Hi all!

In the specs for some A/V receiver with AB amplifiers inside is written SNR 110dB and RMS background noise voltage 250uV. How loud is such noise applied to the speakers? Will be this noise audible? From which distance to the speakers?

Thanks!

The 110db S/N ratio is surely specified at full output level.

At 250uV , S/N ratio would be about 81dB relative to a 1W
output level on a 8 ohm load. (2.828V rms)..

Not a bad value, although a good amp will be have
three times less noise..

81bas · 9th April 2010, 05:43 PM

Ok! Many thanks for the answers!

9th April 2010, 05:07 PM	#1
81bas diyAudio Member Join Date: Jan 2006 Location: Kiel	How loud is 250uV white noise? Hi all! In the specs for some A/V receiver with AB amplifiers inside is written SNR 110dB and RMS background noise voltage 250uV. How loud is such noise applied to the speakers? Will be this noise audible? From which distance to the speakers? Thanks!

9th April 2010, 05:21 PM	#4
event horizon diyAudio Member Join Date: Feb 2008 Location: East Midlands, England	If that spec is real i should imagine there would be the deafening sound of silence within an foot of the speaker. After all that kind of noise will put 0.000000007 W RMS into it Or 7 billionths of a watt __________________ "Never let your morals prevent you from doing what is right!" Salvor Hardin Last edited by event horizon; 9th April 2010 at 05:35 PM. Reason: billionths, not billions lol

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9th April 2010, 05:19 PM	#3
WithTarragon diyAudio Member Join Date: Jun 2007	We do not have enough information yet to guess at this answer. Your speakers will have a specification that translates voltage (usually 2.83 volts) to a dB SPL output at 1m away (sensitivity or perhaps effciency). This will be in the range of 85 to 105 dB per 2.83 volts. At 250 uV you will be about 80 dB below this. Whether this is audible or not can not be determined exactly. Please remember these numers should be weighed against the noise floor in the room iteself. I have not bothered discussing some of the 2nd order effects in this analysis. Others may feel the need to go crazy over htose details. Good Luck, -Tom

9th April 2010, 05:43 PM	#6
81bas diyAudio Member Join Date: Jan 2006 Location: Kiel	Ok! Many thanks for the answers!

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