Imagine you are in an open field where two loudspeakers are set up and connected to the same amplifier so that they emit sound waves in phase at 688 Hz. Take the speed of sound in air to be 344 m/s.

Question

If you are 3.00 m from speaker A directly to your right and 3.50 m from speaker B directly to your left, will the sound that you hear be louder than the sound you would hear if only one speaker were in use?

What is the shortest distance (d) you need to walk forward to be at a point where you cannot hear the speakers?

Answer 1

wavelength=344/688=.5 m
you are from A 7 wavelengths,and from B6 wavlengths. So the sound is inphase from both sources.

To be at a null, the distance has to be 1/2 wavlength (.25 meters) out of sync.

I would move .125meters either way.

I am not exactly certain what "forward" means in the last sentence.