Acoustic

Question: What is audio?
  Answer: Audio is sound frequencies or signals in the audible range. It also refers to the electronic equipment that is used for the recording, transmission, reception, or reproduction of sound. - 187

Question: What is music?
  Answer: Music is an arrangement of sounds in time. - 64

Question: What is music composed of?
  Answer: Music is composed of melody, harmony, rhythm, and timbre. Some music may also include words. - 65

Question: What audio frequencies can be heard by the human ear?
  Answer: The human ear can hear sound wave frequencies in the approximate range of 20 to 20,000 Hertz. - 166

Question: How fast does sound waves travel?
  Answer: At sea level, sound vibrations travel in the air at a speed of approximately 1087 ft. (331 m) per second. - 167