Maths, Physics Revision Physicss Maths Physics Physics A Level Physics Home Maths Maths Revision hut Sound Sound waves are longitudinal waves produced by mechanical vibrations. The amplitude of the wave determines the volume (loudness) of the sound Loud sound Quiet sound The frequency of the wave determines the pitch of the sound Low pitch High pitch Loud speaker The loudspeaker vibrates the air particles and the sound  energy is transferred ECHOES Normally sound vibrations that can be heard by the  human ear are in the frequency range 20 to 20,000 Hz. Frequencies above 20,000 Hz, which cannot be detected by the  human ear are know as ULTRASOUND SOUND CANNOT TRAVEL THROUGH A VACUUM (such as space) Ultrasonic waves are usually produced by electronic systems but are  produced in nature by creatures such as bats which comunicate using ultrasonic signals Uses of Ultrasound Useful link Depth sounding Pre-natal scans Ultrasonic waves are partially reflected at the boundaries of  materials of differing densities the amount of wave reflected depends on the extent of the  difference in density An image of an unborn baby can be built up using theses  reflections Utrasound is also used in medicine to treat gall stones and  kidney stones  Ultrasound is used in industry to scan materials for internal defects and for cleaning Some tooth brushes use utrasonic waves \to clean between  teeth