Sound pressure level (dBA) correction for air temperature /humidity
Sound pressure level (dBA) correction for air temperature /humidity
(OP)
Is there a correction factor for sound pressure level if we want a value at 35°C instead of 25°C which is the actual environment it was measured? Say if we get 45dBA at 25°C, what should be the value at 35°C? Assume no change in air humidity.





RE: Sound pressure level (dBA) correction for air temperature /humidity
So the short answer is no, No correction required.
(Note, I do not work for Bruel & Kjaer)
RE: Sound pressure level (dBA) correction for air temperature /humidity
So, either the calibrator varies bin the same way as the SLM (quite possible), or it isn't making much differnece.
So, having sorted that out, how come the old pistonphone calibrators used to come with a barometer?
Cheers
Greg Locock
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.
RE: Sound pressure level (dBA) correction for air temperature /humidity
all I can guess is that it may depend on the construction of the microphone:
- if it's differential (air pressure acts on both sides of the membrane), it shouldn't be affected by air properties
- if it's sealed-chamber (air pressure acts on one side of the membrane, the other getting to a "sealed" chamber"), then a way must be provided to correlate external air properties with the ones of the fluid (could be air, but not only) in the chamber.
Note: ALL the microphones I dealt with in my life were of the first type...
Regards
RE: Sound pressure level (dBA) correction for air temperature /humidity
RE: Sound pressure level (dBA) correction for air temperature /humidity
RE: Sound pressure level (dBA) correction for air temperature /humidity
ht
Which seems to be part of this site/book ??
http://www.sfu.ca/sonic-studio/handbook/
I will let you do the legwork from here on .
RE: Sound pressure level (dBA) correction for air temperature /humidity
The old B&K Pistonphone was a fixed volume displacement device, so barometric pressure would affect the dynamic pressure it produces. I guess the electrostatic (speaker-type) calibrators in common use today do not have this issue. I still feel compelled to document the temperature, RH, barometric pressure, wind speed, and wind direction when making outdoor sound pressure measurements. Atmospheric parameters have a greater effect on sound propagation than on the measurement instrumentation.
Walt
RE: Sound pressure level (dBA) correction for air temperature /humidity
Cheers
Greg Locock
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.