A bullhorn, also called a megaphone or loudhailer, combines a microphone and an amplified speaker to magnify a human voice. Some bullhorn models are handheld, with the user speaking into a trigger or voice-activated microphone. Other bullhorn types feature a shoulder strap and a keyable microphone similar to a CB radio handset. Both feature a conical loudspeaker which amplifies the voice and sends it out over a considerable distance.
The bullhorn evolved from a non-electrical device called a megaphone. This handheld voice amplifier worked on the principle that sound waves could be concentrated and focused in a cone. College cheerleaders, law enforcement officers, movie directors and military drill teams often used megaphones to amplify their cheers or commands. The modern electronic bullhorn still uses a basic conical design for the loudspeaker. Sensitive microphones have reduced the need to shout into the device, however.
A bullhorn's power output is often measured in watts. A 35 watt bullhorn, for example, is capable of broadcasting a voice over a thousand yards or more. Most bullhorn models do have volume controls, however, so speakers can limit their range when appropriate. Another feature found on some bullhorn models is an attention siren or whistle. This can be effective for crowd control or for commanding attention. The trigger mechanism on a bullhorn can also be locked into position for longer speeches. Some models offer a voice-activated option which will only turn on the microphone when someone is speaking directly into it.
For the ultimate in convenient operation, some bullhorn systems use shoulder straps for portability and a handheld microphone for broadcasts. This keeps the speaker's field of vision from becoming blocked by a standard bullhorn. Police officers often bring a shoulder-supported bullhorn system to events where a quick response may be required.
One drawback to using a bullhorn as a public address system is vocal clarity. Microphones and loudspeakers may electronically 'squash' the natural highs and lows of a human voice. This could lead to a distant or heavily modified sound from the bullhorn. Users must learn to distance themselves a few inches from the microphone screen and to speak very clearly and slowly. Shouting into a powerful bullhorn may also cause distortions and an unpleasant squeal called a 'feedback loop'. Care must also be taken not to get the bullhorn caught between another speaker system. This can also cause a loop to form as the amplfied background noise is fed back into the microphone.
Users of a bullhorn should always respect the rights of others. Individuals may enjoy the protection of free speech, but courts often rule against the use of amplification devices which infringe on other peaceable assemblies. Police officers can enforce noise restriction laws on unauthorized bullhorn broadcasts in public areas.