The minimum intensity of sound is zero at a point due to two sources of nearly equal frequencies when
The minimum intensity of sound is zero at a point due to two sources of nearly equal frequencies when
two sources are vibrating in opposite phase
the amplitude of two sources are equal
at the point of observation, the amplitudes of two SHM produced by two sources are equal and both the SHM are along the same straight line
Both the source are in the same phase
Solution
If two waves of nearly equal frequencies superpose, they give $I_{\text{min}} = 0$, if they both travel in straight line, i.e. $\phi = 0$ and they have equal amplitudes.