Basic acoustics- Complex and waveform analysis

Question 1

What is the difference between an oscillation and a vibration?

Answer 1

Oscillations are back and forth movement around equilibrium due to gravity. Vibrations are back and forth movement around equilibrium due to elasticity

Question 2

Think about the swing of a pendulum. Why does the pendulum swing back and forth when it is displaced?

Answer 2

Inertia and the force of gravity are working against each other

Question 3

Why does the pendulum eventually stop?

Answer 3

Internal friction

Question 4

Since the oscillation made by a pendulum is a sine function, what is the motion often called?

Answer 4

Sinusoidal motion

Question 5

Define periodic motion.

Answer 5

Predictable, repeatable pattern of motion

Question 6

What does the waveform represent?

Answer 6

The behavior of sound as a function of time

Question 7

What does the x-axis represent and the y-axis represent?

Answer 7

The x-axis represents amplitude and the y-axis represents time

Question 8

What is a cycle?

Answer 8

One full repetition of periodic motion

Question 9

What is frequency? How do you calculate it?

Answer 9

Physical measure of sound. Measured by the number of cycles over time in seconds

Question 10

What must be converted (when applicable) in the frequency equation?

Answer 10

Milliseconds must be converted to seconds. 1 ms=.001 s

Question 11

What is period? How do you calculate it?

Answer 11

Time it takes to complete one cycle of vibration

Question 12

What is the relationship between frequency (f) and period (T)?

Answer 12

Frequency and period are inversely related. Frequency is number of cycles over time, where period is time over number of cycles

Question 13

What does phase indicate on a waveform?

Answer 13

One full rotation of the radius around the circle (0* to 360*) results in one complete sine wave

Question 14

Describe an in-phase relationship.

Answer 14

Same frequency, hits the same angles at the same time

Question 15

Describe a 180-degree out-of-phase relationship.

Answer 15

Mirror images, same frequency but hits opposite angles at the same time

Question 16

Describe an out-of-phase relationship.

Answer 16

Same frequency, starts at different times

Question 17

What is the definition of amplitude?

Answer 17

How loud something is

Question 18

What is the range of magnitude changes within one period called?

Answer 18

Peak to peak amplitude

Question 19

The average magnitude for simple harmonic motion is always:

Answer 19

Zero

Question 20

What two forces interact to keep the mass and spring vibrating once it is displaced?

Answer 20

Mass and elasticity

Question 21

Why does the mass and spring model eventually stop?

Answer 21

Internal friction

Question 22

How does force influence the amplitude of the vibration?

Answer 22

The more force that is applied to a system, the more mass that is displaced from equilibrium

Question 23

If force and stiffness of the spring are held constant, but mass is added, what happens to the frequency?

Answer 23

Frequency decreases

Question 24

If force and stiffness of the spring are held constant, but mass is reduced, what happens to the frequency?

Answer 24

Frequency increases

Question 25

If force and mass of the object are held constant, but stiffness in increased, what happens to the frequency?

Answer 25

Frequency increases

Question 26

If force and mass of the object are held constant, but stiffness is decreased, what happens to frequency?

Answer 26

Frequency decreases

Question 27

If mass and stiffness are held constant, but force is changed what happens to the amplitude?

Answer 27

Amplitude increases or decreases

Question 28

Name and define the two forces that interact on the pendulum when set into motion. Describe their role in one cycle of oscillation.

Answer 28

Inertia and gravity. An object is set into motion, overcoming inertia, but gravity fight inertia to bring the object back to equilibrium

Question 29

How are complex vibrations created?

Answer 29

A combination of 2 or more simple waves

Question 30

What are the individual sinusoidal vibrations that make up the complex vibration called?

Answer 30

Frequency components

Question 31

Describe the differences between periodic and aperiodic vibration?

Answer 31

Periodic vibrations are predictable, repeatable patterns. Aperiodic vibrations are not repeatable patterns and motion is random

Question 32

If provided a waveform, how is it calculated by fundamental frequency?

Answer 32

The number of cycles over time in seconds

Question 33

If provided a waveform, how is it calculated by fundamental period?

Answer 33

Time over the number of cycles

Question 34

What is waveform synthesis?

Answer 34

Adding/combining individual sinusoidal components to generate complex sound

Question 35

What is the shape of a complex waveform dependent upon?

Answer 35

Frequency, magnitude, and phase of each component

Question 36

What is the purpose of a Fourier (waveform) analysis?

Answer 36

To breakdown a complex waveform into the individual frequency components

Question 37

What type of graph is generated from a Fourier analysis?

Answer 37

Spectrum

Question 38

What is represented on the x-axis for a Fourier analysis?

Answer 38

Frequency

Question 39

How does a single sinusoidal waveform appear on the spectral display? Why?

Answer 39

As one line, because it is the same frequency

Question 40

How does a complex waveform with many spectral components appear on the spectral display?

Answer 40

Multiple lines

Question 41

Complex aperiodic vibration has so many different components that they do not appear as separate lines on the spectrum. What is the graph called?

Answer 41

Continuous

Question 42

We have formulas for calculating fundamental frequency when provided with a waveform. But what can we use when we are only provided frequency components and not the waveform?

Answer 42

The greatest common factor

Question 43

What is the Greatest Common Factor?

Answer 43

The largest number that is a factor of two or more numbers

Question 44

How do you find the GCF?

Answer 44

Dividing the frequency component by the lowest prime number until prime numbers are all that's left

Question 45

What is a missing fundamental? How can you determine if the fundamental frequency is "missing"?

Answer 45

A frequency that is not equal to or lower than the lowest frequency component provided.