Kenny Andersen, age 11, of Casper, Wyoming, for his question:
WHAT EXACTLY IS HI FI?
Hi fi, also called high fidelity, is a way of reproducing sound with the greatest possible fidelity or faithfulness to the original. Hi fi equipment may be used to reproduce any kind of sound, but it is most often used for reproducing the sound of music.
The best hi fi equipment can make recorded or broadcast music sound almost the way it sounds in a recording studio or concert hall.
A sound reproduction system must meet three requirements before it can be considered to be high fidelity equipment: it must be able to reproduce every musical tone that can be heard in a recording studio; it must reproduce loud tones as clearly as soft ones; and it should not produce any noise or other sound of its own while playing.
Today almost all hi fi sets are built to reproduce stereo, or stereophonic sound. A stereo system adds realism to sounds by reproducing them from their proper direction.
Basic parts of a hi fi system include a program source, an amplifier and a loudspeaker system. The program source can be a record player, an FM radio tuner or tape recording equipment.
The first part of the amplifier that the waves enter is the preamplifier. The preamplifier strengthens the waves and has controls to adjust the volume and tone of the final sound. The other part of the amplifier, the power amplifier, makes the waves powerful enough to operate the speaker system. The speakers change electric waves into sound.
Stereophonic hi fi gives realistic depth and clarity to the sounds by reproducing them from their proper direction. When recording or broadcasting for stereo, engineers use at least two microphones to pick up the sounds made by an orchestra: usually one on the right and one on the left side.
The sound waves picked up by the left microphone then make up the left stereo channel and those picked up by the right make up the right channel. The channels are then combined.
To produce both stereo channels, a hi fi system needs a stereo amplifier which has two amplifiers in one. It also needs two loudspeakers systems. One speaker system reproduces the left channel at the same time that the other speaker system reproduces the right channel.
Engineers have also developed four channel stereo, which reproduces musical echoes from the sides and rear of a recording studio or concert hall, as well as the sounds coming directly from the orchestra.
A hi fi system needs four amplifiers and four speaker systems to reproduce four channel stereo.
Recording studios and radio stations used hi fi equipment during the 1930s, but at that time it was too expensive for home use. The first commercial FM stations appeared in the early 1940s and long playing records became available in 1948. Manufacturers then started to produce home hi fi equipment.
Stereophonic records were introduced in 1958 and created a demand for stereo hi fi equipment. The first multiplex stereo broadcasts took place in 1961.