I purchased two different noise level meters (SPL). They both have a resolution of +-1.5 dB but when I turn them on (both on the dBA scale and near each other in the same room, same noise, both on either fast or slow time weighting) their readings are different, not by just a couple of dBs.
Why? Is that to be expected? Which one is giving the more correct reading? How would I know?
Post by Michael Lawrence on Nov 19, 2018 21:04:51 GMT
Correct, pasim! SPL meters need to be calibrated. Also, chaos01, are they SPL meters or "noise meters?" They are not the same thing. A calibrated random incidence mic will not give the same result as a calibrated free field mic, and both types are used for certain types of SPL measurements.
That kasuntest is pretty cheap, so i wouldn't trust its calibration, also don't understand what that 94db @ 1khz means here, something to do with its accuracy?
One DIY way to "calibrate" those meters is, if you have some apparatus that has LwA dB rating, for example air compressor, lawn mower. You just put the meter really close to the source and try to match the reading.
I wonder if there is an online app that output a sound of specific db so I can cross test my two sound level meters.
I purchased one of them on amazon: KASUNTEST Professional Sound Level Meter Digital Noise Tester Range:30 to 130dB with Large LCD Display and Backlit
The only thing you can do is produce a signal with a static RMS value. That won't help you calibrate an SPL meter because your monitors need to be set to a known value also. This is the whole basis of the K System and I have a video on it here. If anything, I'd just download an app and calibrate your meter to that since I assume those microphones are well-calibrated at the factory.
Post by Michael Lawrence on Nov 21, 2018 23:38:29 GMT
There is a somewhat expensive device called a pistonphone that produces a highly calibrated SPL, usually 1 Pa (94 dB SPL) but sometimes 114, and they are the "right" way to calibrate an SPL meter if you don't want to send it back to the factory. It's a specialty purchase though.