Section 3

Question 1

What are complex waves?

Answer 1

Characterized by a combination of different frequencies, amplitudes, and phase relationships. Can be periodic or aperiodic.

Question 2

What does periodic mean?

Answer 2

Wave repeats over time and has a musical or tonal quality (musical notes, sustained vowels in speech)

Question 3

What does aperiodic mean?

Answer 3

Wave does not repeat itself over time and has more of a “noise” type quality (transient sounds in speech and environment)

Question 4

How do frequencies work in a periodic complex sound?

Answer 4

All frequencies are whole number multiples of the fundamental frequency (harmonic series)

Question 5

What is the fundamental frequency?

Answer 5

the lowest frequency of vibration in a harmonic series

Question 6

Explain harmonics

Answer 6

Any whole number multiple of the fundamental frequency

Question 7

How does the fundamental frequency relate to the first harmonic?

Answer 7

They are the same number, since the fundamental frequency can be multiplied by itself.

Question 8

How do you find the second harmonic?

Answer 8

The second harmonic is twice the fundamental, the third three times the fundamental, the fourth four times the fundamental, etc.

Question 9

What is an overtone?

Answer 9

Any component in a complex tone having a frequency higher than the fundamental- the first overtone is equal to the second harmonic, etc.

Question 10

What is a partial?

Answer 10

Indicates a part of partial of the complex tone or harmonic series- the fundamental frequency is also the first partial

Question 11

What is an octave?

Answer 11

Any interval of two frequencies having a frequency ration of 2:1 (a doubling of the frequency)

Question 12

Do harmonics all have equal amplitudes?

Answer 12

No, even though fundamental frequency determines all harmonic frequencies.

Question 13

What is the result of two waves of different frequency and/or amplitude being generated simultaneously?

Answer 13

A new wave that is the sum of each of the separate waves.

Question 14

What is a steady state sound?

Answer 14

Frequency, composition, amplitude and phase relationship of the partials of a tone are constant over time- usually periodic.

Question 15

What is a transient sound?

Answer 15

A change in steady state- usually aperiodic.

Question 16

What is a Fourier analysis? How is it represented? What is on this representation?

Answer 16

Shows that any complex sound can be broken down to show the individual sinusoidal components of that sound. Represented on a graph called a spectrum that shows the amplitude, frequency, and phase of each individual sine wave in a complex sound.

Question 17

What is an amplitude spectrum?

Answer 17

The ordinate will indicate the range of amplitudes, the abcissa will indicate the range of frequencies

Question 18

What is a phase spectrum?

Answer 18

Can also be plotted to show the starting phase of each individual sine wave

Question 19

What does each line on a spectrum represent?

Answer 19

An individual sine wave that is part of the complex sound (therefore the line will inherently represent the individual sine waves amplitude, frequency, and phase.

Question 20

What is interference?

Answer 20

The phenomenon that occurs when two waves meet while traveling along the same medium. The interference of waves causes the medium to take on a shape that results form the net effect of the two individual waves.

Question 21

What is constructive interference?

Answer 21

A type of interference where two interfering waves have a displacement in the same direction. Can occur where the two interfering waves are displaced upwards, or when they are displaced downward.

Question 22

What occurs when two interfering waves are in phase? (Started at the same phase and were identical in amplitude and frequency)

Answer 22

Would result in summation of the two waves and a doubling. Ex: If a sine wave with a max displacement of -1 interferes with a sine wave with the same frequency with a max displacement of -1 unit, the the resulting wave in the medium is a sine wave with a max displacement of -2 units.

Question 23

What is destructive interference?

Answer 23

Where two interfering waves have displacement in opposite directions. If a sine wave with a max displacement of +1 meets with a sine wave of -2, then the resulting displacement will be -1. If two interfering waves of the same frequency and amplitude meet but are 180 degrees out of phase, the waves will cancel each other out- resulting in no sound.

Question 24

Explain what a beat is

Answer 24

When two sound waves of almost identical frequency combine, the alternating constructive and destructive interference causes the sound to be alternatively soft and loud- sounding like it is “beating.”

Question 25

What is “noise”

Answer 25

Noise is a sound that has little or no periodicity- a sound with instantaneous amplitude that varies over time in a random manner.

Question 26

What is white noise?

Answer 26

All frequencies in a a specific range are present, regardless of phase, and the average power over a frequency range is constant. Average power is equal to the product of the frequency range and intensity.

Question 27

What is pink noise?

Answer 27

Amplitude decreases by one half with each doubling of frequency

Question 28

What is a low pass filter?

Answer 28

Attenuates high frequencies and passes low frequencies

Question 29

What is a high pass filter?

Answer 29

Attenuates low frequencies and passes high frequencies

Question 30

What is a combination filter?

Answer 30

A combination of a low and a high pass filter to pass a specific range of frequencies (narrow band or speech noise)

Question 31

What is a transient sound?

Answer 31

Speech, that is not steady, is a series of transient sounds. Transient sounds are aperiodic and change frequently.

Question 32

How did white noise get it’s name?

Answer 32

White noise gets it’s name from white light. All frequencies within a specific range are present regardless of the phase and all the intensities are the same. There will be single line at each frequency when looking at the spectrum.

Question 33

What is an ordinate on a spectrum?

Answer 33

Refers to an element plotted on the vertical axis and tells us the amplitude/intensity of sound

Question 34

What is an abcissa on a spectrum?

Answer 34

The horizontal axis of a spectrum, tells us the time.

Question 35

How common are pure tones? What are most sounds?

Answer 35

Not common in nature at all, usually complex sounds