sentence: Sound waves are converted into an electrical signal inside the recorder.
sentences_before: In the late 1930s the tape recorder appeared. Tape recorders use a magnetic tape as a medium, with a 'recording head' to store the sound on the tape.
sentences_after: This signal goes into the head, where it changes the polarity of very small magnets. Tape moves past the head at a constant speed, and its magnetic particles are rearranged by these magnets to a pattern that represents the sound wave. These magnetic patterns are much like the small grooves of a cylinder or disc record in the way that they represent the vibration energy of sound waves.
concept_name: sound wave
headings: Sound recording Technology Tape
categories: Sound