The working standard Model 378B02 is more stable in extreme environments than the low cost Model 130 series. Model 130 microphones will experience larger shifts in sensitivity caused by temperature, humidity and atmospheric pressure. Both microphones should be calibrated in the test environment after they have stabilized. The accuracy of the measured DATA MAY be affected by the PLACEMENT position and/or the geometry of the microphone and any reflections that may be present. The effect of the microphone itself on the sound field at the point of measurement (1/4’’ vs. 1/2’’ microphone) can alter the measurement. If this occurred, then change the position of the microphone and perform another measurement. If the error is only at higher frequencies, it is important to note that the specification of the 130E20 at 10 kHz is ± 2dB. The model 377B02 is flatter to 20 kHz. Variations WITHIN tolerance may occur in SPECIFIC instances. 

The working standard Model 378B02 is more stable in extreme environments than the low cost Model 130 series. Model 130 microphones will experience larger shifts in sensitivity caused by temperature, humidity and atmospheric pressure. Both microphones should be calibrated in the test environment after they have stabilized. The accuracy of the measured data may be affected by the placement position and/or the geometry of the microphone and any reflections that may be present. The effect of the microphone itself on the sound field at the point of measurement (1/4’’ vs. 1/2’’ microphone) can alter the measurement. If this occurred, then change the position of the microphone and perform another measurement. If the error is only at higher frequencies, it is important to note that the specification of the 130E20 at 10 kHz is ± 2dB. The model 377B02 is flatter to 20 kHz. Variations within tolerance may occur in specific instances.