The following animation represents a cross section of a three-dimensional sound

Question

The following animation represents a cross section of a three-dimensional sound wave propagating away from a moving source. The circles represent successive peaks of the waves. There are five different animations, each with a different source velocity. Clicking inside the Animation box will give you the x and y coordinates (in meters) of the point that you click. The time shown in the animation is in msec (1x10-3). You may assume that all the waves travel at the same velocity. The following animation represents a cross section 1) What is the frequency of the emitted sound wave in Animation 1? 500 Hz 1000 Hz 2000 Hz 3000 Hz 2) What is the velocity of the sound wave in Animation 1? 250 m/s 500 m/s 750 m/s 1000 m/s 1250 m/s 3) What frequency of sound would a stationary observer hear if they were located to the right of the source in Animation 2? 700 Hz 1000 Hz 1429 Hz 1526 Hz 1830 Hz 4) What frequency of sound would a stationary observer hear if they were located to the left of the source in Animation 3? 556 Hz 750 Hz 1000 Hz 1256 Hz 1800 Hz 5) A stationary observer to the right of the source in Animation 4 would hear: No sound ,Sound at a very high frequency ,Sound at a very low frequency

Explanation / Answer

1) animation 1

x = 1.3 m

number of waves = 5

t = 6.5 ms

hence

f = n/t = 5/6.5*10^-3 = 769.2307 Hz

hecne f is more than this as more than 5 waves have been produced ( but less than 6)

hence

f < 923.07684 Hz

f > 769.2307 Hz

hence approximately

f = 1000 Hz

2) velocoty of sound in animation 1 = v

v = lambda*f

lambda = 1.3 m

hence

v = 1300 m/s

so option 1250 m/s

3) in animation 2, for a perosn to the right of the source

f' = v/lambda'

also

f' = f(v/(v - u))

u = (2.4 - 0)/(8.1 - 0)*10^-3 = 296.2962962 m/s

hence

f' = 1310.6796116504 Hz

closest option 1429 Hz

4) for left of the animation position

f' = f(v/(v + u)) = 808.383233583276 Hz

closest option 750 Hz

5) animation 4 as the source moving at the speed of sound in the medium

so any person to the right of the source will hear no sound and will hear sound only after the source has crossed the observer

Related Questions

Navigate

• Browse (All)
• Browse T
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.