00:01
So we have in -phase loudspeakers with the same amplitude.
00:08
That's going to mean that they're identical sources.
00:15
They're separated by a distance d.
00:19
And the frequency is 170 hertz.
00:39
So we want destructive, complete destructive interference.
00:47
We get complete destructive interference when delta x equals lambda times m plus one half, where m is 0, 1, 2, 3.
01:09
So delta x is the distance between the speakers.
01:15
Now, the speed of sound were given as 340 meters per second.
01:27
Speed equals wavelength times frequency.
01:31
And so wavelength is speed over frequency.
01:35
And so delta x is speed over frequency, which in this case, 340 divided by 170 v divided by f is 2 times m plus 1 1ā2.
01:53
So again, this is just 2 times m plus 1ā2...