The Collaborative International Dictionary
Phonometer
Phonometer \Pho*nom"e*ter\, n. [Phono- + -meter.] (Physics) An instrument for measuring sounds, as to their intensity, or the frequency of the vibrations.
Wiktionary
phonometer
n. An instrument for measure sounds.
Wikipedia
Phonometer
A phonometer is an instrument invented by Thomas Edison for testing the force of the human voice in speaking. It consists chiefly of a mouthpiece and diaphragm. Behind the diaphragm is placed a delicate mechanism which operates a 15-inch flywheel by means of which a hole can be bored in an ordinary pine board.