Here is the original question and the first part:
Two speakers are set up 13.5m apart in an auditorium, pointing at each other. A pure sound of frequency 256Hz is being played through them. You may assume that the phase difference of the signals as they arrive at the speakers is 0∘. A person is standing on the line joining the speakers, 0.25m from the mid point. The speed of sound in air is 330ms −1. Calculate the phase difference as it would be detected by the person.
I got the correct answer for that part of 2.4, and the wavelength(in case needed for the second part of the question) was 165/128m.
I’m unsure however as to how to complete the second half of this isaac physics question:
The person moves to the mid point between the speakers (where the sound is loudest due to constructive interference), and then walks towards one speaker until the sound waves cancel out. How far do they walk until they find this point of near silence?
I know it will be destructive interference and so the phase difference should be 180degrees but when I used this in the equation Phase Diff. = (pi2 x Path Diff.)/Wavelength to be able get the path difference, my answer of 0.64m was incorrect and it said “Think carefully about how the path difference changes as the person moves - the distance travelled by the sound from one speaker increases while the distance travelled by the sound from the other speaker decreases.
Remember that you are now looking for destructive interference, not constructive interference.“ But I thought I had done destructive interference.
Any help would be really appreciated.