How Does a Sound Meter Interpret Different Frequency Ranges?

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SUMMARY

The discussion centers on the functionality of sound meters, specifically how they interpret different frequency ranges using dB (A) and dB (C) scales. A sound meter measures total sound power, but the dB (A) scale applies a filter that focuses on specific frequency ranges, resulting in lower readings compared to the total sound pressure level (SPL). The dB (C) scale, on the other hand, emphasizes low frequencies, which can lead to instances where the dB (C) reading exceeds the dB (A) reading, despite the total SPL being constant. This discrepancy arises because the two scales measure different aspects of sound frequency response.

PREREQUISITES
  • Understanding of sound pressure levels (SPL)
  • Familiarity with dB (A) and dB (C) weighting scales
  • Basic knowledge of sound power measurement
  • Concept of frequency spectrum analysis
NEXT STEPS
  • Research the differences between dB (A) and dB (C) weighting in sound measurement
  • Learn about sound spectrum analyzers and their applications
  • Explore the principles of sound power level calculations
  • Investigate the impact of frequency response on sound meter readings
USEFUL FOR

Acoustics engineers, sound technicians, and anyone involved in noise measurement and analysis will benefit from this discussion.

fisico30
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Hello Forum,

I am planning to buy a noise meter.
This instrument receives a signal that carries a certain total power. A spectrum analyzer tells us how this total power is distributed among the various frequency components.

When the sound meter gives a reading in the dB (A) scale it is practically applying a filter to that frequency spectrum and giving us the area (power) contained only in those frequencies. For example, if 100 dB SPL of sound hit the noise meter the reading will probably be less dB than 100 because the meter only cares about a certain frequency range...

dB (C) focuses on the low frequencies...

Question: If the meter is in front of a noise source, the dB reading on the dB (C) scale can be larger than the reading on the dB (A) scale. The dB(A) and dB(C) reading don't sum up to 100 dB SPL? why not? For instance, could it be that we read 60 dB(A) and 90 dB(C) even if the sound hitting the meter is 100 dB SPL...
Thanks,
fisico30
 
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It is basically a pressure measurement.

Sound power level ##P=20log(\frac{P}{P_{ref}})##

Where Pref is the reference or hearing threshold pressure.
 

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