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                                          FACTS ABOUT SOUND




                   The speed of sound is                                    343 m/s

                   The audible range of sound in human                      20 Hz to 20,000

                   beings is                                                Hz
                   The level of sound prolonged exposure                    85 dB

                   beyond which may cause permanent
                   hearing loss

                   A woman’s voice is shriller than a man’s                 Pitch
                   voice because of higher

                   The animals which produce sounds of                      Dolphins and
                   high pitch and frequency to communicate                  elephants

                   and locate each other
                   The loudness of sound is measured in                     Decibels

                   Stringed instruments have boxes attached                 Loudness of the

                   to increase the                                          sound produced
                   The minimum distance which is required                   17 metres

                   to hear an echo

                   The system of sound reflection used to                   SONAR (Sound
                   find the depth of oceans                                 navigation
                                                                            ranging)

                   The phenomenon which makes the sound                     Doppler effect
                   of an approaching train shriller

                   Sounds cannot travel in vacuum

                   Sounds travel faster in metals than in air

                   Sonic boom occurs when a super sonic aircraft crosses the
                   sound barrier
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