Question

Two pianos each sound the same note simultaneously, but they are both out of tune. On a day when the speed of sound is 348 m/s, piano A produces a wavelength of 0.766 m, while piano B produces a wavelength of 0.780 m. How much time separates successive beats?

Answer 1

Lamda = c * T
T = L/c
f = 1/T = c/L

f1 = 348/.766 = 454.3 Hz
f2 = 348/.780 = 446.2 Hz

difference beat frequency = 8.15 Hz
period of beat frequency = 1/8.15 = .123 s

Answer 2

find each frequency by f=speedsound/wavelength

Now, find the beat frequency f1-f2

Now find the time between beats !/beatfrquency