From: liz@poppyrecords.invalid.invalid   
      
   Scott Dorsey  wrote:   
      
   > In article <10gsa0o$d26a$1@dont-email.me>, Tobiah   wrote:   
   > >The Rode NT1-A lists an "Equivalent Noise Level" of 5 dBA.   
   >   
   > This is meaningless and cannot be compared between other microphones because   
   > no two manufacturers measure under the same conditions.   
   >   
   > >So I can look at that figure, and compare it to other mics.   
   > >But then I thought, what about sensitivity?  If the noise   
   > >figure measures the raw noise level coming into the preamp,   
   > >then a high sensitivity mic would have a larger signal to   
   > >noise ratio, making the self noise figure meaningless on   
   > >its own.  Or does the noise figure take that into account   
   > >somehow?   
   >   
   > The noise level should be the noise just of the microphone, which under   
   > most conditions is going to swamp the noise of the preamp unless the   
   > microphone sensitivity is so very very low.   
      
   The resistive component of the source impedance of the microphone is   
   another source of noise.  From the Rode NT1-A specification I have   
   calculated this to be about 10dB below the noise level they quote, so it   
   is insignificant in this case.  In some other mics, which were intended   
   for close singing, the resistance of the moving coil was the biggest   
   noise source.   
      
   It would be instructive to test it in a vacuum and see how much of the   
   total noise is caused by Brownian motion of the air molecules.  This   
   becomes a significant limiting factor with small diaphragm area mics.   
      
      
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   ~ Liz Tuddenham ~   
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