Sound and hearing



Sound :  The sound is a mechanical vibration ( an oscillation ) transmit by the air to our ears ( or a microphone ) .  The frequency of this oscillation is


expressed by the unit Hertz ( Hz ) that means an oscillation by second . The human ear can understand  frequencies between 20 Hz and 20.000 Hz .













Speed : The sound move at a speed of  340 meters by second in the air , what explains the phenomenon of echo and that we see a lightning of storm before to hear it .


The LA :  The frequency of note LA , that serves as reference to tune musical instruments ,  is 440 Hz .  This is also the telephone’s  tonality ( in France ) .


The ear:  Sounds have a scale of sounding pressure very great .  Thereby the ear has a conversely proportional reply per sound volume .


The ear does not understand bass and trebles on the same manner according to the volume of the sound .  More the sound is strong more the basses and trebles are heared .


Basses :  Bass sounds are channeled by walls ( ground, ceiling ) that increases their relative level ( x2 to x4 ) .  The worse places are the corners of rooms .


It is necessary to think at preceding remarks , if we want to make an opinion concerning a sound reproduction , and to listen at a volume equal to the reality .


Trebles :  Mediums sounds and trebles are rather directives .  They have the feature to be reflected by walls ( reverberation, echo ) .


The ear:  The age of a person , or the fact that it has been submitted to high sound pressures , decreases the perception of the sound ( mainly of  treble sounds ) .


Tinnitus :  A person that has been submitted a long time to heavy sounds has also ears that whistle all the day .


Silence :  The perfect silence does not exist .  There is always a little noise .  In all manner in a total silence we can hear the noise of the blood circulating in ears .