G.R.A.S. Sound & Vibration
Pistonphone Types 42AA/42AA-S1 - Page 5
The Pistonphone works on the principle of two reciprocating pistons actuated by a precision-
machined cam disc with a sinusoidal prole. The rotation speed of the cam disc is controlled to
within 0.5% via a tachometer signal in a feed-back loop.
The operating procedure is straight forward, simply t the microphone into the coupler of the
Pistonphone and switch on. The Pistonphone will now produce a constant sound pressure level
on the diaphragm of the microphone.
The Pistonphone is normally delivered with a coupler for calibrating ½-inch microphones. Adapt-
ers for calibrating ¼-inch and ⅛-inch microphones are included. A coupler (RA0023) for calibrat-
ing 1-inch microphones is also available.
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