sentence: Pitch is how humans hear different frequencies.
sentences_before: Pitch' is the highness or lowness of sound.
sentences_after: Frequency is determined by the number of vibrations per second. The highest key on a piano, for instance, vibrates 4,000 times per second. Lower keys have lower frequencies. A note an octave higher than another note has twice the frequency of that note.
concept_name: pitch
headings: Sound Sound Pitch and Intensity
categories: Basic English 850 words