G.R.A.S. 44AA Mouth Simulator is a sound source which simulates the sound field around the human mouth at close quarters and complies with the Standards IEEE 269, 661 and ITU-T Rec. P51.
G.R.A.S. 44AA is for testing telephone mouthpieces as well as other microphones similarly used in communication networks.
At the mouth reference point (MRP), which is 25mm from the detachable lip ring (35mm from the mouth of the G.R.A.S. 44AA), the maximum continuous signal it can produce in 1/3-octave bands is 100dB re. 20µPa in the frequency range 100Hz to 16kHz. Its loudspeaker accepts an external signal either directly or via its own built-in power amplifier (when power is applied).
Jigs are included for calibration according to CCITT P.51 and IEEE 269. These are for use with 1/4″ or 1/2″ microphones. One jig holds the microphone at 0º incidence (1/4″ only) to the sound source, the other at 90º incidence (1/4″ or 1/2″).