Chapter 21

How many octaves exist between 40 hertz and 1280 hertz?

5

What is meant by the fundamental frequency of a musical note?

A partial tone at the lowest frequency

Distinguish between analog and digital for how the sound signal is captured on phonograph records versus a CD?

Analog recordings on a record store a continuous trace of motion, whereas digital recordings on a CD record digital values sampled many times a second

What did Fourier discover about complex periodic wave patterns?

Complex periodic signals can be disassembled into a sum of simple sine waves

Which makes central use of the binary system?

DVDs

What feature of sound is measured in decibels?

Intensity

How do the loudest sounds we can tolerate compare with the faintest sounds?

The loudest sounds are a trillion times more intense

Why are there normally more violins than trombones in an orchestra?

Violins are not as loud as trombones

The pitch of a note has most to do with

frequency

A decibel is a measure of a sound's

loudness

One person has a threshold of hearing of 5 dB, and another of 10 dB. Which person has the more acute hearing?

the one who can hear 5 dB

How many decibels correspond to the lowest-intensity sound we can hear?

0 decibels

How does the intensity of a 30-dB sound compare with the intensity of a sound at the threshold of hearing?

1,000 times more intense

Compared to a sound of 40 decibels, the intensity of a sound of 50 decibels is

10 times as much

When sound at 60 decibels is boosted to 80 decibels, the sound has about

100 times the intensity

How many octaves exist between 100 hertz and 1600 hertz?

4

If the fundamental frequency of a note is 200 Hz, then what is the frequency of the second harmonic?

400 Hz

How many octaves exist between 20 hertz and 2560 hertz?

7

The frequency of a note on octave higher in pitch than a 440-Hz note is

880 Hz

The fundamental frequency of a violin string is 440 hertz. The frequency of its second harmonic is

880 hertz

The graphs shown in (Figure 1) represent pressure variation versus time recorded by a microphone. Which could correspond to a sound wave?

BC (B & C --The one that looks like a "W" and the one that is crazy squiggly lines) (NOT the straight line)

How does a high-pitch musical note relate to frequency?

High pitch is how the ear perceives high frequencies

Consider three notes: A 123 Hz; B 721 Hz; and C 458 Hz. Rank them from highest to lowest for *frequency*.

Highest B 721 Hz C 458 Hz A 123 Hz Lowest

Rank them from highest to lowest for *pitch*

Highest B 721 Hz C 458 Hz A 123 Hz Lowest

Which of these can be most accurately measured?

Intensity of sound

A certain sound is recorded by a microphone. The same microphone then detects a second sound, which is identical to the first one except that it has twice the *frequency*. In addition to the higher frequency, what distinguishes the second sound from the first one?

It is perceived as higher in pitch

A certain sound is recorded by a microphone. The same microphone then detects a second sound, which is identical to the first one except that the *amplitude* of the pressure fluctuations is larger. In addition to the larger amplitude, what distinguishes the second sound from the first one?

It is perceived as louder.

Rank them from longest to shortest for *wavelength*.

Longest A 123 Hz C 458 Hz B 721 Hz Shortest

Having established that a sound wave corresponds to pressure fluctuations in the medium, what can you conclude about the direction in which such pressure fluctuations travel?

Pressure fluctuations travel along the direction of propagation of the sound wave.

Based on the information presented in the introduction of this problem, what is a sound wave?

Propagation of pressure fluctuations in a medium

Why does the use of blue light make it possible to store more information on a DVD?

Shorter-wavelength blue light can be focused to a smaller spot, allowing more bits to fit in the same area

A violin string playing the note "A" oscillates at 440 . What is the period of the string's oscillation?

T = 2.3 ms

In the oscilloscopes shown, which screen displays the louder sound (assuming detection by equivalent microphones)?

The pattern on the right. (kind of looks like two mountains)

Which of the two musical notes displayed one at a time on an oscilloscope screen has the higher pitch?

The pattern shown on the left. (it has a more patterned look. Like 4 and a half mountains)

Musical tones are characterized by

all of the above (quality, loudness, pitch)

Which of these sounds characterize "white noise"?

all of the above (surf, bubbling water, rustling leaves)

Digital signals for music are a direct measure of sound

amplitutde

Fourier analysis is something accomplished

both of these (with all musical instruments, automatically by humans)

Fourier analysis is based on the finding that all sound waves

can be represented as a series of simple sine waves

As we become older, the frequency range of human hearing

decreases

The next graph in (Figure 2) shows a sound wave consisting of a sinusoidal displacement of air particles versus time, as recorded at a fixed location. For sinusoidal waves, it is possible to identify a specific frequency (rate of oscillation) and wavelength (distance in space corresponding to one complete cycle). Taking the speed of sound in air to be 344 m/s, what are the frequency f and the wavelength λ of the sound wave shown in the graph?

f, λ = 1000,0.344 Hz,m

The quality of a musical note has to do with its

harmonics

In all musical instruments, quality of sound depends on the

number and relative loudness of the partial tones

Each note on a piano keyboard has its own

pitch

What most distinguishes noise from music is the presence of

regularity

What varies between two tones that are different in timbre, that is, two tones that have the same fundamental frequency but are produced, say, by different musical instruments?

the harmonic content

The pitch of a note on a guitar string can be increased by increasing the

tightness of the string

Compared with the first harmonic of a musical note, the second harmonic has

twice the frequency

Double the frequency of a musical note and you halve its

wavelength

Does air play a role in the propagation of the human voice from one end of a lecture hall to the other?

yes

What is the wavelength of the lowest sounds we can hear, about 20 Hz?

λ = 17 m

The highest frequency humans can hear is about 20,000 Hz. What is the wavelength of sound in air at this frequency?

λ = 17 mm