Chapter 3

Question 1

What is vibration? What’s another name for it?

Answer 1

A back-and-forth movement, known also as oscillation

Question 2

Explain a cycle of vibration, accounting for displacement and restorative forces, and equilibrium.

Answer 2

A vibration cycle involves an initial force causing the movement of an object, disrupting equilibrium. This is the displacement force. The restorative force, the force working to bring the object back into equilibrium, attempts to bring the object back to its original resting state. With the example of a ball and spring contraption, the displacement force moves the ball and spring out of its resting position, and when let go, the restoring forces pull it in the opposite direction. But because of inertia, the tendency of an object to want to stay in motion, it overshoots the original position of rest, and the cycle continues until the vibration cycle loses energy because of frictional forces.

Question 3

What is a mechanical wave?

Answer 3

A wave that needs a medium through which to transfer energy

Question 4

What are pulse waves?

Answer 4

Pulse waves are a type of mechanical wave that describe a single disturbance traveling through a medium

Question 5

What is a longitudinal pressure wave?

Answer 5

A longitudinal pressure wave is a repeated cycle of pressure disturbances in which the particles of the medium travel parallel to the direction of the wave

Question 6

What are compressions and rarefactions?

Answer 6

Areas of high collision and areas of high separation of air particles caused by displacement and restorative forces

Question 7

What are the two ways by which energy can be transferred in a wave?

Answer 7

Energy can be transferred by the wave itself (like a domino effect) or by the particles in the wave

Question 8

How is energy transferred in a sound wave?

Answer 8

Energy is transferred by wave, as it is a motion of connecting particles

Question 9

What is frequency?

Answer 9

Frequency is how fast the particles of a sound wave vibrate each second

Question 10

What is period?

Answer 10

A period is the time between successive points of pressure in a wave

Question 11

What is the relationship between frequency and period?

Answer 11

They are reciprocals, so a high-frequency sound wave will have a small period, and a low-frequency sound wave will have a larger period.

Question 12

What is intensity?

Answer 12

Intensity is the power per unit area (how much power is transferred from one particle to another)

Question 13

How are pressure and amplitude of vibration related to intensity?

Answer 13

The greater the power of a sound wave, the greater its amplitude… intensity increases as the square of the amplitude of the sound pressure. So if amplitude is doubled, intensity is quadrupled

Question 14

What is the inverse square relationship?

Answer 14

The inverse square relationship is the relationship between intensity and distance from the source. They are inversely related, so by whatever factor distance increases, intensity decreases by that same factor. So if the distance from the source is doubled, intensity is quartered

Question 15

How do we measure intensity?

Answer 15

We measure intensity as the relative power of one sound to another sound, measured in decibels of sound pressure level (dB SPL)

Question 16

Why do we use a logarithmic scale when measuring intensity?

Answer 16

Because there is such a wide range of intensities that can be detected by the human ear, and using a logarithmic scale allows us to simplify the range and work with these larger numbers

Question 17

Define wavelength.

Answer 17

Wavelength is the distance traveled during one cycle of vibration (so one cycle of compression and rarefaction)

Question 18

What factors can influence the speed of a sound wave?

Answer 18

Altitude (air density), state of matter, and temperature (speed of molecule movement)

Question 19

What properties of soundwaves do not affect speed?

Answer 19

Frequency and wavelength do not affect the speed of sound. The speed can only be changed by the qualities of the medium through which it is traveling

Question 20

How does pitch relate to fundamental frequency?

Answer 20

Pitch is the perception of frequency

Question 21

How does loudness relate to intensity?

Answer 21

Loudness is the perception of intensity

Question 22

What is the semitone scale?

Answer 22

The semitone scale is a chromatic scale composed of 12 tones, each separated by a semitone (a half step up or down)

Question 23

Define complex wave.

Answer 23

A complex wave is a wave composed of several different frequencies

Question 24

What is the fundamental frequency of a complex wave composed of the following three frequencies: 100 Hz, 350 Hz, and 500 Hz?

Answer 24

The fundamental frequency of this complex wave would be 50 Hz because it is the fundamental frequency of the lowest component sine wave.

Question 25

What defines a complex wave as periodic? Nearly periodic?

Answer 25

A complex wave is periodic when the component sine waves all have a mathematical relationship between them and have a consistently repeating waveform pattern for each cycle. A complex wave is nearly periodic when it has some slight variability.

Question 26

Define the appearance of a periodic waveform.

Answer 26

A periodic waveform has a repeating pattern and a consistent waveform with each new cycle

Question 27

What is a power spectrum?

Answer 27

A power spectrum is a graph that represents the power of a wave using amplitude and frequency (without time represented)

Question 28

Line and continuous spectra represent what types of sounds, respectively?

Answer 28

Line spectra represent complex periodic waves, and continuous spectra represent noise

Question 29

Define constructive and destructive interference.

Answer 29

Constructive interference refers to an interaction between two compressions or rarefactions of two different waves, causing an amplification. Destructive interference occurs when the compression of one wave meets the rarefaction of another wave, canceling out the compressions and rarefactions (leaving a lack of sound)

Question 30

Describe the two types of behaviors that can occur when a sound wave meets a boundary within the vocal tract.

Answer 30

Reflection, which is basically when the sound bounces back off of a surface it encounters, and transmission, which is when the sound goes through a boundary rather than bouncing off of it or going around it

Question 31

Explain the concept of natural resonant frequency.

Answer 31

Natural resonant frequency is the frequency at which an object vibrates the easiest and with the greatest amplitude. So using a swing as an example, if the person pushing the swing pushes at the point where the frequencies are similar, then there will be a higher amplitude

Question 32

How is the natural resonant frequency of an object affected by its stiffness, mass, and length?

Answer 32

Stiffness affects how much displacement force is required to move mass. So an increased stiffness will cause a higher frequency, and increased mass a lower frequency. Length also affects the rate of vibration. So all three, affecting the rate of vibration, influence the natural resonant frequency of an object

Question 33

What is a standing wave?

Answer 33

A standing wave is a wave that appears to stand still due to an interference pattern where both the incident wave and the reflected wave have the same frequency

Question 34

What are nodes and antinodes?

Answer 34

Nodes are the lowest points of amplitude in a standing wave, and antinodes are the highest points of amplitude in a standing wave

Question 35

Explain the difference between free and forced vibration.

Answer 35

Free vibration occurs when an object can vibrate freely after the initial disturbance, while forced vibration occurs when the vibration of the object occurs due to the vibration of another outside oscillator

Question 36

Under what conditions would you expect the vibration of one object to result in a strong (large amplitude) vibration of a second object? Under what conditions would you expect a weak (small amplitude) vibration to result?

Answer 36

You would expect the vibration of one object to result in a strong vibration of a second object when the frequencies of vibration of the two are very similar. You would expect a weaker vibration when the frequencies are dissimilar

Question 37

What is the difference between a mechanical and an acoustic resonator? Which type of resonator is the vocal tract?

Answer 37

An acoustic resonator is a resonator in which the air inside of a container or space is fully or partially enclosed. A mechanical resonator, such as a tuning fork, is not contained. The vocal tract is an acoustic resonator because there is at least partial enclosure of air