How does sound remain on phonograph records?
A flat record disk may hold the jolly jive of a jazz band, Or it may hold the resounding beauty of a full symphony orchestra. It is a prison of sounds. High notes, low notes, loud notes arid soft notes are locked in a tiny groove. The key to release them is a small needle held in the arm of the record player,
Lets examine the groove on a record, It runs in one continuous spiral from the outside towards the center.. If we magnified it we would see that it is a very wavy little path. It swings arid sways in a wavy route side to side. In some places it swoops in wide curves, In others‑the waves are riot so wide. This waving from side to side makes the difference between loud and soft notes. The loud notes come forth as the needle runs around the big wide waves, The soft notes come out as the needle glides around the more gentle waves. Some of the waves in the groove come close together. Others curve gradually and the distances are longer from curve to curve, This causes the difference between high and low notes. The high notes come forth as the needle wobbles from side to side along the closely packed waves, The low notes come forth when the needle glides along the long$ gentle waves,.
Early phonographs were wound by a handle. This tightened a spring which set the turntable and its record spinning around, Sometimes the machine ran down in the middle of a record, The merry music would drop down to a low groan and come to a stop,
The low groan happened because the needle was moving too slowly to make an accurate copy of the recorded music, Not only must the disk have a wavy groove to record the differences in loudness and pitch the needle must be set to travel along the groove at exactly the right speed.
A super modern phonograph can travel at different speeds to play different types of records, The turntable can be switched to spin at 45 or 33 1/3 revolutions a minutes The old standard disks are recorded to play at 78 revolutions per minute. A long‑playing 12‑inch record is made to give 332 minutes of music turning at 33 1/3 revolutions per minute.
A record is made as sound waves jog a cutting tool. A turntable spins as the tool cuts the wavy groove into a soft disk, The pitch of each notes the high or low of it has its own wave length, This wave length is called frequency, The. tool cuts high frequency sounds in wide waves, It cuts low frequency sounds in narrow gentler waves.
The wave frequency of middle C is 256, That is the number of waves the phonograph needle must cover every second to give off a middle C note. That is why the turntable speed must be just right, If the note is loud the 256 waves will be wide ones if soft they will be narrow. Notes below middle C have fewer waves per second, Higher notes have more waves per second.