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how sound or noise are measured in decible?

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smartshashi

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I am working on microcontroller based db meter which measures the signal strength of sound or noise in decibel.I want to know what technique uses the sound or noise measuring intruments available in market.
The formula for db is
db(v1/v2)=20log base10(v1/v2)
I want to know how this formula is implemented in sound or noise measurement as both are measured in decibel.
 

1. Attached pdf will explain all about dB
2. Take in account that for acoustic measurements you must to use
weight filter (A- curve, for example) that have frequency response
inverse to human ear
2. Log calculation may be too heavy for small processor,
so better to use hardware conversion - log amplifier (from Analog or TI)
 

Sound pressure level is a logarithmic measure of the energy of a particular noise relative to a reference noise source. It's expressed in dB compared to a reference source of 20 µPa (micropascal)

Lp = 20 × log (ρ1 / ρo)

where:

ρo = 20µPa Noise Reference
ρ1 = noise you're measuring

so you'll need a well know sound pressure level to calibrate your system,
or just borrow another dB meter.

Regards
 

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