Question

A fly buzzes past you at 6 m/s. The frequency of the buzz made by its wings is 162 Hz. Assume the speed of sound to be 334 m/s. What is the observed frequency of the hum as the bumblebee approaches you?

Answer 1

f'=(u/u-us)f where u is the speed of sound us is the speed of the source and f is the frequency made by the buzz

Answer 2

i dont really understand

Answer 3

if you hear the siren of an ambulance coming towards you wont you hear a slightly different frequency when it is near you?

Answer 4

wont it be a little higher?

Answer 5

http://en.wikipedia.org/wiki/Doppler_effect go to that page down down on the right there is a file listen to that

Answer 6

this is a car horn of a car coming towards you if you listen carefully you will see that the horn when the car is approaching is a little higher in frequency and then lower and lower

Answer 7

oh okay thank you. :)

Answer 8

you listened to the difference?:D

Answer 9

yes

Answer 10

one is higher than the other

Answer 11

yes look there is a very subtle difference in the middle if you can listen very carefully it starts higher and then a little bit higher! and then lower lower lower

Answer 12

can you listen where it goes a little bit higher?

Answer 13

yes i can hear and see where it goes a little bit higher and lower

Answer 14

nice...when it is a bit higher the car is near you...i mean it starts away from you and when it is near you it is a little bit higher and when it goes away it is lower

Answer 15

your problem deals with the part that the car (or the buzz) comes towards you ...so you hear the frequency a little bit higher

Answer 16

so when the car is near me its going to be a louder than it was when it was farther away from me?

Answer 17

no not louder ...higher frequency...i will explain you that

Answer 18

higher frequency=higher pitch=someone singing in higher notes than some other for example

Answer 19

it doesnt mean he is singing louder

Answer 20

when the car is near you it is not louder it is in higher pitch

Answer 21

okay

Answer 22

want me to explain it with wave theory terms or practically?

Answer 23

i mean i can explain to you why for example the wavefronts are being reduced but i dont know if you want to understand it that way

Answer 24

can we try the wave theory terms?

Answer 25

you know the basics of wave theory?

Answer 26

i mean wavelength,frequency how are they connected etc.

Answer 27

ok probably not...imagine a boat coming toward you and you listen to the engine...if you see the sea you will see some circular ripples right?

Answer 28

on the spot of the boat as it is moving...right?

Answer 29

yes

Answer 30

imagine the boat coming towards you and those ripples being reduced constantly..or well let me draw it

Answer 31

something like that

Answer 32

oh okay

Answer 33

ok now those ripples you see at the sea are the same as the circular wavefronts produced by the engine

Answer 34

that means the sound wavefronts

Answer 35

okay

Answer 36

as the boat moves closer to you you will see the ripples at the sea =the sound wavefronts like this right?