Two loudspeakers ( L₁ and L₂ ) are placed with a separation of 10 m, as shown in figure. Both speakers are fed with an audio input signal of same frequency with constant volume. A voice recorder, initially at point A , at equidistance to both loud speakers, is moved by 25 m along the line A B while monitoring the audio signal. The measured signal was found to undergo 10 cycles of minima and maxima during the movement