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Re: spectrum level to RMS

Assuming a uniform spectrum level within the band the noise is measured:
Spectrum Level = Band Level - 10 log(noise bandwidth in Hz).
Incidentally, both of these are RMS values - the differentiation is that one of these RMSs is a "band level" and the other "spectrum density level". Also, these should be in the same units (both SPL, both db A, etc). Similarly, the RMS values should be obtained using the same averaging time (presumably "long" in your application).

On 6/20/2011 10:01 AM, Merri J. Rosen wrote:
Hello all,

I'm looking for a particular formula related to calibration.  Noise amplitudes are often reported in spectrum level (aka equivalent SPL), i.e., the sound intensity in a 1kHz band, often reported as dB/Hz.  I am calibrating my noise by directly measuring its RMS (in pascals), and calculating dB SPL from there.  I would like a formula that converts spectrum level (dB/Hz) to RMS (assuming you know the bandwidth of the noise), in order to be able to relate spectrum level to my calculated dB SPL.  Any suggestions are appreciated.


   Merri J. Rosen, Ph.D.
   Assistant Professor, Department of Anatomy&  Neurobiology
    NEOMED (Northeast Ohio Medical University)
    Office: 330/325-6516     Lab: 330/325-6633

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