Question
There are three sources of sound of frequency 248 Hz, 250Hz and 252 Hz. Find the number of beats observed per second when all are sounded together.
Solution
Let the amplitude of waves from three sources be a.
Let v = 250 Hz.
Therefore 248 = v–2 and 252 = v+2.
When the three waves superimpose, the resultant wave is,
The amplitude of resultant wave is,
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which is maximum when 
where, n = 0, 1, 2, 3...
That is,
Time interval between two maximum is![<pre>uncaught exception: <b>mkdir(): Permission denied (errno: 2) in /home/config_admin/public/felixventures.in/public/application/css/plugins/tiny_mce_wiris/integration/lib/com/wiris/util/sys/Store.class.php at line #56mkdir(): Permission denied</b><br /><br />in file: /home/config_admin/public/felixventures.in/public/application/css/plugins/tiny_mce_wiris/integration/lib/com/wiris/util/sys/Store.class.php line 56<br />#0 [internal function]: _hx_error_handler(2, 'mkdir(): Permis...', '/home/config_ad...', 56, Array)
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.
Thus, the frequency of maximum is 4.
Hence, the number of beats heard per second when all the three sources are sounded together is 4.
Let v = 250 Hz.
Therefore 248 = v–2 and 252 = v+2.
When the three waves superimpose, the resultant wave is,
The amplitude of resultant wave is,
which is maximum when where, n = 0, 1, 2, 3...That is,
Time interval between two maximum is
. Thus, the frequency of maximum is 4.
Hence, the number of beats heard per second when all the three sources are sounded together is 4.
