DESIGN AND CONSTRUCTION OF AUDIO MEGAPHONE

DESIGN AND CONSTRUCTION OF AUDIO MEGAPHONE

ABSTRACT

1.0                                                        INTRODUCTION
Megaphone amplifies a person’s voice or other sounds and direct it in a given direction. The sound is introduced into the narrow end of the megaphone, by holding it up to the face and speaking into it, and the sound waves radiate out the wide end. An electric megaphone is a handheld public address system, an electronic device that amplifies the human voice like an acoustic megaphone, using electric power. It consists of a microphone to convert sound waves into an electrical audio signal, an amplifier powered by a battery to increase the power of the audio signal, and a loudspeaker to convert the audio signal to sound waves again. Although slightly heavier than acoustic megaphones, electric megaphones can amplify the voice to a higher level, to over 90 dB. They have replaced acoustic megaphones in most applications, and are generally used to address congregations of people wherever stationary public address systems are not available; at outdoor sporting events, movie sets, political rallies, and street demonstrations.
Although electronic public address systems have existed since vacuum tube amplifiers were developed in the early 1920s, vacuum tube versions were too heavy to be portable. Practical portable electric megaphones had to await the development of microelectronics which followed the invention of the transistor in 1947. In 1954, TOA Corporation developed the EM-202, the world’s first transistorized megaphone.
Handheld versions are shaped generally like the old acoustic megaphone, with a microphone at one end and a horn speaker at the other, and a pistol grip on the side, with a trigger switch to turn it on. In use, the device is held up to the mouth, and the trigger is pressed to turn it on while speaking. Other larger versions hang from the shoulder on a strap, and have a separate handheld microphone on a cord to speak into, so users can address a crowd without the instrument obscuring their faces. A vast array of modern electric megaphones are available to purchase, and characteristics like power, weight, price, and the presence of alarms and shoulder straps all contribute to a consumer’s choice.
The shape of the megaphone directly affects the range of projection; narrower horns compensate for lower power by concentrating sound more sharply than wide horns. Megaphone speaking-trumpet, bullhorn, or loud hailer is a portable, usually hand-held, cone-shaped acoustic horn.

1.1                                         BACKGROUND OF THE PROJECT
For decades, film directors have used megaphones to communicate with their cast and crew on sets where it was hard to hear. Cecil B. DeMille, director of epic movies like The Ten Commandments and The King of Kings, was the first director to use a megaphone during production. Many of his films were biblical epics set on vast outdoor sets that required communication with hundreds of extras. The acoustic megaphone became a clichéd symbol of a movie director, although modern directors use electric megaphones.
The distinctive distorted sound of a human voice amplified by a megaphone is widely recognized, from its use in train and bus stations and sports arenas. Applied to music, it gives the sound of an antique acoustic gramophone record player. It has been used in radio advertisements and popular music to give retro and often humorous effects. A recorded voice or music can be processed to give it a “megaphone” sound effect without using an actual megaphone, by audio recording decks and software. In recording software like Logic Pro and Pro Tools, selecting certain filters and settings will produce an artificial sound almost indistinguishable from an electric megaphone.
1.2                                             OBJECTIVE OF THE PROJECT
The objective of this work is to provide a novel and improved portable megaphone, said device providing a controlled amount of amplification of the users voice and being simple in construction, easy to handle, and light in weight.

1.3                                         SIGNIFICANCE OF THE PROJECT
This megaphone is widely used for crowd management and mass communication. When needing to transmit important information or to guide a large number of people, an electric megaphone is valuable if other public announcement systems are not present. Besides their practical implications, public address systems, including megaphones, also had a social impact. Public address systems helped promote women’s participation in society.
1.4                                                 SCOPE OF THE PROJECT
This work provide an improved electric megaphone device incorporating its own amplifier and power supply, said device involving relatively inexpensive components, being rugged in construction, being compact in size and being arranged so that the volume of sound output and the energization of the device can be controlled by one of the users hands which at the same time supports the rear portion of the megaphone while his other hand may be employed to balance or to support the forward portion of the megaphone.
1.5                                           LIMITATION OF THE PROJECT
During the process of using a megaphone, the sound of the voice is a bit distorted because of the frequency differences between the voice and the megaphone. Over the past several decades, the voice powered megaphone has in many cases been replaced by electric powered bullhorns. However, the voice distortion remains part of the package.

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