A phonometer is an instrument invented by

Thomas Edison Thomas Alva Edison (February 11, 1847October 18, 1931) was an American inventor and businessman. He developed many devices in fields such as electric power generation, mass communication, sound recording, and motion pictures. These inventio ...

for testing the force of the human voice in speaking. It consists chiefly of a

mouthpiece Mouthpiece may refer to: * The part of an object which comes near or in contact with one's mouth or nose during use ** Mouthpiece (smoking pipe) or cigarette holder ** Mouthpiece (telephone handset) ** Mouthpiece (woodwind), a component of a woodw ...

and

diaphragm Diaphragm may refer to: Anatomy * Thoracic diaphragm, a thin sheet of muscle between the thorax and the abdomen * Pelvic diaphragm or pelvic floor, a pelvic structure * Urogenital diaphragm or triangular ligament, a pelvic structure Other * Diap ...

. Behind the diaphragm is placed a delicate mechanism which operates a 15-inch

flywheel A flywheel is a mechanical device which uses the conservation of angular momentum to store rotational energy; a form of kinetic energy proportional to the product of its moment of inertia and the square of its rotational speed. In particular, ass ...

by means of which a hole can be bored in an ordinary pine board.

References

External links

* American inventions Thomas Edison Physiological instruments {{measurement-stub