Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. 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 towards a targeted direction. This is accomplished by channeling 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. 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 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.

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