Two speakers with opposite phase are positioned 3.5 apart, both pointing toward
ID: 2152046 • Letter: T
Question
Two speakers with opposite phase are positioned 3.5 apart, both pointing toward a wall 5.0 in front of them (see the figure). An observer standing against the wall midway between the speakers hears destructive interference.
Explanation / Answer
When the listener moves the distance to one speaker is sqrt(4.5^2 + (1.6-.84)^2) = 4.564m and the distance to the other is sqrt(4.5^2 + (1.6+.84)^2) = 5.119m So the separation distance is 5.119 - 4.564 = 0.5552m Therefore ? = 2*0.5552m = 1.11m Since v = ?f then f = v/? = 343m/s/1.11m = 309Hz