Two microphones, two devices, two different results

crawford

I have two mics--micW i436 on a new MacBook Pro M3 and i437L on iphone XR. They are both calibrated the same. When doing simultaneous measurements, the Sound meters give different answers, say 102 and 109 dB. However, the both give the exact same frequencies using FFT. The frequencies are always the same, though not the same for the vertical dB magnitude axis. All settings are the same for both tools in each device. Both tools are set for single impulses with same trigger. The tools are loaded in the multitool in both cases. Is this normal, fixable, or operator error? Also, the trigger units for FFT and oscilloscope ... are they Pa? Thank you in advance.

benfaber

When doing simultaneous measurements, the Sound meters give different answers, say 102 and 109 dB.

The differences in measured levels can be due to a number of factors, including microphone frequency response, the acoustical environment in which the measurements are made, the microphone positions within that environment, the nature of the sound being measured, etc.

The frequencies are always the same, though not the same for the vertical dB magnitude axis.

I'm not sure what this means. Perhaps, you could include a screenshot to help clarify what you are seeing.

Is this normal, fixable, or operator error?

It's normal in the sense that making acoustical measurements can be quite challenging. It's easy to get bad data, or, in other words, it can take significant effort to make sure you are measuring precisely what you intend to.

the trigger units for FFT and oscilloscope ... are they Pa?

The trigger threshold units match the trigger source channel. If the source is Self, then each selected channel will self-trigger with the threshold in it's own units.
So, if you have input channels with units of Pa selected in the FFT and Oscilloscope tools, their trigger thresholds will be in Pa.