Two audio speakers are kept some distance apart and are driven by the same amplifier system. A person is sitting at a place 6.0 m from one of the speakers and 6.4 m from the other. If the sound signal is continuously varied from 500 Hz to 5000 Hz, what are the frequencies for which there is a destructive interference at the place of the listener? Speed of sound in air` = 320 ms^-1`

Answer

`1200 Hz,2000 Hz,2800 Hz,3600 Hz,4400 Hz`

Explanation

`(2pi)/(lamda) Delta = (2n +1) pi`
For destructive interference
`(2pi)/(v)f(6.4-6)=(2n+1)pi`
`rArrf=((2n+1))/(0.8)=400(2n+1)(v=320m//s)`
`=400Hz,1200Hz,2000Hz,`
`2800Hz,3600Hz,4400Hz`