1)The fundamental of an organ pipe that is closed at one end and open at the oth

Question

1)The fundamental of an organ pipe that is closed at one end and open at the other end is 261.6

Hz(middle C). The second harmonic of an organ pipe that is open at both ends has the same frequency.

a)What is the length of the pipe that is closed at one end and open at the other end?

b)What is the length of the pipe that is that is open at both ends?

2)Cracking Your Knuckles When you "crack" a knuckle, you cause the knuckle cavity to widen rapidly. This, in turn, allows the synovial fluid to expand into a larger volume. If this expansion is sufficiently rapid, it causes a gas bubble to form in the fluid in a process known as cavitation. This is the mechanism responsible for the cracking sound. (Cavitation can also cause pits in rapidly rotating ship's propellers.)

If a "crack" produces a sound with an intensity level of 56

dB at your ear, which is 20cm from the knuckle, how far from your knuckle can the "crack" be heard? Assume the sound propagates uniformly in all directions, with no reflections or absorption.

Explanation / Answer

Wavelenth is speed / frequency.

The organ pipe (open at one end) has its fundamental at 4 times the length of the pipe. So set length at wavelength / 4.

a)

wavelength=343/261.6

=1.311m

L=1.311/4

=0.327m

b)

length of the pipe that is that is open at both ends

L=lamda/2

=1.311/2

=0.655

2)

beta=10log(I2/I0)

56=10log(I2/I0)

5.6=log(I2/I0)

398,107=A1/A2

D=126.19m

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