Module 8: sound in tubes

Question 1

What restricts the ability of air molecules to move around during resonation ?

Answer 1

Tubes

Question 2

Chose the TWO that true regarding tubes:

1. When Determining the resonant frequency , we must consider the length of the tube.
2. The width of the tube divided by the frequency yields us the amount of air particles within the object when both sides are closed
3. Whether the tube is open or closed at each end effects the resonance of the tube
4. Closed objects resonant at higher frequencys than those with both ends closed.
5. If a tube is closed at one end, the air particles at the closed end move faster than the air particles at the open end

Answer 2

1 and 3

Question 3

If a tube is open at both ends, the air particles can move in and out freely at both ends. True or false.

Answer 3

True

Question 4

What happens to the air particles when a tube is closed at one ends?

Answer 4

The air particles at the closed end cannot move past the closure and pressure builds up there. The particles bounce back towards the opening creating a standing wave.

Question 5

The lowest frequency that can produce a standing wave in a tube that is closed at one end is:

Answer 5

a wavelength that is 4x the length of the tube.

Question 6

Why is it that the wavelength of the fundamental frequency of a standing wave has to be 4x the length of the tube?

Answer 6

Because we only need a point of equilibrium (which is at the opening of the tube) and a point of maximum pressure( which is at the closed end of the tube) to fit in the tube to create the resonance.

Question 7

True or false: A tube closed at one end resonants at EVEN harmonics of its fundamental frequency?

Answer 7

False: A tube closed at one end resonants at ODD harmonics of its fundamental frequency?

Question 8

:)

Answer 8

keep up the good work

Question 9

In order to determine the resonant frequencies of a tube that is CLOSED AT ONE END, you would? What about if you are trying to find a specific harmonic?

Answer 9

Divide the speed of sound by FOUR TIME the length of the tube.
To find a specific harmonics, you would then multiple the quotient by the harmonic number you want to find.

Question 10

When sound enters a tube that is open at both ends, pressure is released at the open ends of the tube. Equilbrium happens at the openings. True or false

Answer 10

True

Question 11

What is the fundamental frequency of a completely open tube?

Answer 11

Wavelength of resonant frequency is 2x the length of the tube

Question 12

True or False: Open tubes resonate at ALL HARMONICS

Answer 12

True

Question 13

To find the frequencies when both ends of a tube are open you ? What about finding a specific harmonic?

Answer 13

divide the speed of sound by 2x the length of the tube. To find each harmonic, just multiply this quotient by the harmonic that you wish to find.

Question 14

True or false:
A tube that is open at both ends and a tube that is closed at both ends, will have the SAME RESONANT frequencies. . The resonant frequency has a wavelength twice the tube length.

Answer 14

TRUE

Question 15

When both sides are closed, equilibrium happens where?

When both sides are open, equilibrium happens where?

Answer 15

Closed: Pressure can build against each wall (compression against one wall and rarefaction against the other wall). Equilibrium is established in the middle.

Open: Pressure is released at both ends and this allows equilbrium to be maintained at both openings.

Question 16

Your vocal tract behaves like a tube that is closed at one end. It resonants only at ODD HARMONICS of the fundamental frequency. True or false

Answer 16

TRUE

Question 17

Which of the following tubes would resonante at only odd harmonics of the fundamental frequwncy

a) a tube with both ends closed
b) a tube with one end closed
c) a tube with both ends open

Answer 17

b) a tube with one end closed

Question 18

When a standing wave is created in a tube with an open end, why does equilibrium form at the opening?

a) because pressure builds at the closed end
b) the air particles can move freely in and out of the tube
c) the air particles are trapped and cannot escape

Answer 18

b) the air particles can move freely in and out of the tube

Question 19

Which of the following tubes would have a fundamental frequency with a wavelength four times its length?

a) a straw that has been pinched off at one end
b) a pipe open at both ends

Answer 19

a) a straw that has been pinched off at one end