Sound Definitions

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Sound definitions:

Decibels (dB) -  a measure of how much energy a sound carries 

[how strong it is].  A conversation is 60 dB, 

a noisy restaurant is 70 dB and a rock concert is 120 dB.

Infrasound - a sound below what humans can hear.  

Scientists have discovered that elephants communicate using low sounds 

that humans can’t hear.  Their low rumblings produce very long sound 

waves that travel far across forests and grasslands.

Ultrasound - a sound above what humans can hear.  

These very high sounds are used by bats, porpoises and some kinds of 

insects to communicate.