Pressure Field Microphone Data

[IvanArk]

I am using DAQ assistant to record audio data from two microphones (Type 4966 and Type 4944-A from B&K). The latter is a pressure field microphone. For the other, free-field microphone the data is centered at 0 amplitude and seems to fluctuate between 0.4 to -0.4 Pa in ambient noise. Data from the pressure field microphone doe not seems to be centered at 0 and fluctuates from 0.4 to ~-2 for the same data. Is this expected? The only difference between the two microphones when setting up the DAQ assistant is changing the sensitivity.

I am a bit unfamiliar with pressure field microphones and their behavior, so I was not sure if this is typical for this type of microphone or if I am missing some setting/configuration. 

[dsb@NI]

Ambient noise data makes for a difficult compare. No screenshots and no code makes for a vague response.

Readings at low/ambient levels might be expected to be different depending on the noise floor of each sensor and the relative position and orientation of each sensor to the sound source(s). The sensor models that you referenced have grossly different (>50X) measurement ranges and sensor sensitivities.

First, verify that you have configured each channel appropriately for your sensor. While acquiring, generate some interesting sounds that you can correlate between channels. Clap, snap, whistle, play a tone from your phone. If both mics are responding as expected, you have probably configured each correctly. If you have a calibrator, verify that each sensor measures the expected calibration level.