Megaphone

For other uses, see Megaphone (disambiguation).

A late 19th-century speaking trumpet.

An electronic megaphone.

A megaphone, speaking-trumpet, bullhorn, blowhorn, or loud hailer is a portable, usually hand-held, funnel cone-shaped device whose application is to amplify a person’s voice towards a targeted direction. This is accomplished by channeling the sound through a funnel, 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. The trade-off is that if a listener is to the side, it is more difficult to hear what is being said. An electronic megaphone amplifies sound to a higher decibel level. 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.

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.

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

See also

• Horn (acoustic)
• Horn loudspeaker