Two loudspeakers, a and b, are driven by the same amplifier and emit sinusoidal waves in phase. the frequency of the waves emitted by each speaker is 172 hz. you are 8.00 m from speaker a. take the speed of sound in air to be 344 m/s. part a what is the closest you can be to speaker b and be at a point of perfectly destructive interference? express your answer in meters.