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This frequency weighting is commonly used for peak sound levels plus
entertainment and machinery noise.
D-Weighting
This frequency weighting is intended to adjust the signal frequency spectrum to
match the sensitivity of an average human ear for sound pressure levels
between approximately 50 and 90dB.
It is similar in response to B-weighting but is improved upon by including an
allowance for ear canal resonance at frequencies between approximately 2kHz
and 5kHz.
This frequency weighting is generally used for the high level measurement of
aircraft noise.
Like B-weighting it is not commonly used and is not available on Castle
instrumentation.
Flat-Weighting
This frequency weighting does not adjust the signal frequency spectrum and has
been superseded by Z-weighting because the flat frequency pass band is not
governed meaning different responses between manufacturers of sound meter
instrumentation.
Z-Weighting
Another commonly used frequency weighting filter that has a very flat frequency
response only adjusting the signal frequency spectrum below approximately
10Hz and above approximately 20kHz.
This weighting replaces Flat-weighting so that sound meter manufacturers all
had the same pass band limits.
A common use for this weighting is to determine adequate hearing protection
as well as for peak measurement.