There is an amazing diversity of sounds around us. The number of vibrations per second of a sound gives it its pitch and the strength of the vibrations determines its loudness.

Birdsong is high pitched.	A watch ticking is even higher in pitch but much softer.
A construction worker's jackhammer is low pitched.	An aircraft engine is even lower in pitch but much louder.

Although our ears are very sensitive they are limited in their ability to hear all types of sound. Our ears can hear from about 20 to 20,000 vibrations per second. The low notes of bass musical instruments are around 100 vibrations per second while high notes from flutes and tin whistles are about 1,000 vibrations per second. Bats use sound waves as high as 50,000 vibrations per second but these are outside of our human range (ultrasonic).

The Edison Phonograph 

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