The G.R.A.S. 42AP Pistonphone is a battery-operated, precision sound source for accurate and reliable calibration of measurement microphones, sound level meters and other sound measuring equipment.
Typical applications and use
Reference calibration source
Precision microphone calibrations
Microphone comparisons
P-I index measurement at 250 Hz or 251.2 Hz
Calibration indepenent of atmospheric pressureand altitude