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Comparing noise levels



 
 
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  #1  
Old December 23rd 19, 05:29 PM posted to rec.audio.pro
Tobiah
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Default Comparing noise levels

Say one mic has a self-noise figure of 5dBA, and
another is 10dBA. How much louder is the noise
going to be from the second mic, both electrically
and perceptually?
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  #2  
Old December 23rd 19, 05:42 PM posted to rec.audio.pro
Mike Rivers[_2_]
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Default Comparing noise levels

On 12/23/2019 12:29 PM, Tobiah wrote:
> Say one mic has a self-noise figure of 5dBA, and
> another is 10dBA.* How much louder is the noise
> going to be from the second mic, both electrically
> and perceptually?


Well, 5 dB different, in theory one being almost twice as noisy as the
other. But those are pretty low noise figures. You'd need a good bit of
gain in order to hear the mic noise at all.


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  #3  
Old December 23rd 19, 05:47 PM posted to rec.audio.pro
Tobiah
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Posts: 644
Default Comparing noise levels

On 12/23/19 9:42 AM, Mike Rivers wrote:
> On 12/23/2019 12:29 PM, Tobiah wrote:
>> Say one mic has a self-noise figure of 5dBA, and another is 10dBA.
>> How much louder is the noise going to be from the second mic, both
>> electrically and perceptually?

>
> Well, 5 dB different, in theory one being almost twice as noisy as
> the other. But those are pretty low noise figures. You'd need a good
> bit of gain in order to hear the mic noise at all.
>
>


The magnitude of the numbers was arbitrary. Doesn't some sort of
logarithm come in to play with dB? I remember something about xdB being
perceptually twice as loud as ydB, but I didn't think that y/x == 2.
  #4  
Old December 23rd 19, 05:58 PM posted to rec.audio.pro
Scott Dorsey
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Default Comparing noise levels

In article >, Tobiah > wrote:
>Say one mic has a self-noise figure of 5dBA, and
>another is 10dBA. How much louder is the noise
>going to be from the second mic, both electrically
>and perceptually?


Unknown, unless you know what methods were used under what conditions. This
is one of the things that is not at all standardized.

Now... if they are both from the same manufacturer then you can expect that
the noise will be perceptually 5dB higher on one microphone than the other.
Electrically? You don't know and you can't even really guess without knowing
the spectrum of the noise since the dBA measurement is very heavily weighted.
--scott


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"C'est un Nagra. C'est suisse, et tres, tres precis."
  #5  
Old December 23rd 19, 06:07 PM posted to rec.audio.pro
Mike Rivers[_2_]
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Posts: 2,135
Default Comparing noise levels

On 12/23/2019 12:47 PM, Tobiah wrote:
> The magnitude of the numbers was arbitrary.


Oh!

> Doesn't some sort of
> logarithm come in to play with dB?* I remember something about xdB being
> perceptually twice as loud as ydB, but I didn't think that y/x == 2.


dB is all about logarithms. I'm sure there's an article about it on my
web site. You can use this handy on-line calculator, which also shows
you the formulas:
http://www.sengpielaudio.com/calculator-db.htm

But as Scott says, there's no sure way to compare noise specifications
from manufacturers' literature because they don't all measure it in the
same way. Some day there will be an AES standard, but still, not
everyone will adhere to it.

See the article about microphone specifications on my web site for more
general information about what microphone noise might mean.



--
For a good time, call http://mikeriversaudio.wordpress.com
 




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