Megaphone

Megaphone
A late 19th-century speaking trumpet.
An electronic megaphone.

A megaphone, speaking-trumpet, bullhorn, blowhorn, or loud hailer is a portable, usually hand-held, cone-shaped horn used to amplify a person’s voice or other sounds towards a targeted direction. This is accomplished by channelling the sound through the megaphone, which also serves to match the acoustic impedance of the voice cords to the air. The natural human voice tends to spread evenly in all directions, whereas when it is sent through a megaphone, the sound is concentrated in a given direction and the coupling of its energy to the air optimised,[1] while if a listener is to the side, it is more difficult to hear what is being said.

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History

Though some instrument of the kind appears to have been in earlier use, the origin of the megaphone, or speaking trumpet as it was called, is connected with the name of Athanasius Kircher and that of Sir Samuel Morland, who in 1670 proposed to the Royal Society of London the question of the best form for a speaking trumpet. Johann Heinrich Lambert, in the Berlin Memoirs for 1763, seems to have been the first to give a theory of the action of this instrument, based on an altogether imaginary analogy with the behaviour of light.[2]

A later, papier-mache trumpet of special design was the Sengerphone.[3]

The first such device with the name Megaphone was an invention of Thomas Edison.[4][5]

Electric megaphones

In 1954, TOA Corporation developed the EM-202, the world's first electric megaphone.[6]

An electronic megaphone amplifies sound to a higher decibel level. It can be amplified from over 90 dB. It consists of a microphone, an amplifier and a loudspeaker. Common uses for megaphones are at sporting events, political functions, and generally when one needs to address congregations of people in open spaces.

See also

References

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