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Acoustics I: Basic Physics > Section 2 > Flashcards

Section 2 Flashcards

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1
Q

What is amplitude

A

The maximum displacement of the body from it’s position of equilibrium

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2
Q

What is peak to peak amplitude?

A

The maximum displacement in one direction plus the maximum displacement in the other. (Includes a compression and a rarefaction)

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3
Q

What will greater amplitude show on a sine wave?

A

Higher compression and greater displacement

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4
Q

What is the psychological correlate of amplitude?

A

Loudness

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5
Q

What is frequency?

A

The number of complete vibrations or cycles per unit of time. Measured in cps and expressed in Hz.

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6
Q

What is the frequency range of an average human?

A

20-20,000 Hz. Below this is infrasonic, and above this is ultrasonic.

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7
Q

How does mass affect frequency?

A

As mass increases, frequency decreases. As stiffness of a system increases, frequency increases.

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8
Q

What is resonant frequency?

A

The natural rate of vibration for a mass

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9
Q

Can all mass be set into a vibration other than it’s resonant frequency?

A

Yes, but when the force is removed, it will revert to it’s resonant frequency until it is damped.

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10
Q

What is the psychological correlate of frequency?

A

Pitch

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11
Q

Define period

A

The time elapsed during a single complete vibration

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12
Q

How does a period correspond with frequency?

A

They are reciprocals. A period= 1/f Low frequency sounds have a long period, high frequency sounds have a short period.

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13
Q

What is phase

A

Describes vibratory and wave motion when comparing waves- a cycle of a wave can be compared to a circular motion- 360 degrees is one wave cycle

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14
Q

What is a wave’s phase at equilibrium?

A

0

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15
Q

What is a wave’s phase at maximum compression?

A

90

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16
Q

What is a wave’s phase at 2nd equilibrium?

A

180

17
Q

Does a wave’s starting phase always have to start at 0 in phase?

A

No.

18
Q

What is velocity? How is it determined?

A

The speed at which sound travels. Determined by the density of the medium- more dense molecules have higher sound velocity- therefore, sound travels through a solid faster than through a liquid or gas. Reduced at higher altitudes and increased in higher temperature and humidity.

19
Q

What is the velocity of air?

A

1130 ft/sec or 344 m/sec

20
Q

What is wavelength?

A

The distance between two identical points on two adjacent waves- Wavelength is velocity of sound divided by the frequency (w=v/f)

21
Q

As frequency increases, wavelength…

A

Decreases

22
Q

What type of frequency has a short wavelength? What type has a long wavelength?

A

High frequency has short, low frequency has long

23
Q

What is damping? What causes it? How does it relate to amplitude?

A

A reduction in amplitude over successive oscillations- when vibrations decay over time. Occurs due to friction and absorption of sound. Causes a decrease in amplitude over time, while frequency is unaffected.

24
Q

If you know the wavelength of a pure tone, how could you solve for frequency?

A

f=c/w

25
Q

What is free vibration?

A

When no outside force is perpetuating the vibration. Examples are tuning forks, pendulums, vibrating strings… It will vibrate at it’s own natural resonant frequency.

26
Q

What is forced vibration?

A

An outside force controls the vibration of an object- vibration will continue until the outside force is removed.

27
Q

What happens when a source of energy is removed from forced vibration?

A

Object will revert to free vibration until it is damped. Ex: human ear highly damped to avoid continuing vibration after a sound.

28
Q

Is frequency affected by amplitude?

A

No.

29
Q

What is the display of a sine wave waveform called?

A

Time-domain waveform

Acoustics I: Basic Physics (4 decks)

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