Appendix A - Nature of Sound

Question 1

Describe the nature of sound.

Answer 1

Sound comprises acoustic energy transmitted through a medium and perceived by a receiver in the form of sound waves.

Question 2

What are sound waves and how are they created?

Answer 2

Sound waves are compression waves created by a physical vibration source and move through the air to a receiver.

Question 3

Define frequency in the context of sound waves.

Answer 3

Frequency is the number of times per second the cycle of the sound wave repeats, measured in Hertz (Hz).

Question 4

How can a basic sound wave be understood more easily?

Answer 4

A basic sound wave can be understood more easily by looking at a simple sine wave, representing the repeating cycle of high pressure (crest) and low pressure (trough).

Question 5

What are the five basic qualities of sound waves?

Answer 5

Frequency, wavelength, amplitude, waveform, and phase.

Question 6

Describe the frequency range for musical pitches.

Answer 6

Musical pitches are usually below 8,000 Hz, within the range of 20 Hz to 20,000 Hz.

Question 7

Define wavelength in the context of sound waves.

Answer 7

Wavelength is the physical distance covered by one complete cycle of a sound wave, calculated by dividing the speed of sound by the frequency.

Question 8

What is amplitude in the context of sound waves?

Answer 8

Amplitude reflects the energy in the sound wave and is most closely related to volume and dynamic.

Question 9

How is amplitude measured and what are the limits of human hearing in decibels?

Answer 9

Amplitude is measured in decibels (dB SPL), with 0 dB SPL being the limit of human hearing and 130 dB SPL being the threshold for pain.

Question 10

Describe the waveform in the context of sound waves.

Answer 10

Waveform is the shape of the sound wave, which varies based on the source of the sound and its physical properties.

Question 11

Describe the composition of most musical tones in terms of fundamental and harmonics.

Answer 11

Most musical tones are composite sounds with one prominent fundamental tone and many nearly inaudible overtones, also called partials or harmonics.

Question 12

What is the term used for the first harmonic in a composite sound?

Answer 12

The first harmonic is also called the fundamental.

Question 13

How are harmonics produced in a vibrating string on a stringed instrument?

Answer 13

When a string is plucked, it vibrates along its total length producing a prominent fundamental tone, but also vibrates in pieces independently, causing many nearly inaudible harmonics.

Question 14

Define the harmonic series in the context of musical tones.

Answer 14

The harmonic series is a regular pattern of harmonics produced by smaller vibrating segments of a string, representing different fractions of the whole string (e.g., 1/2, 1/3, 1/4), and forms the acoustic basis for Western European scales and chords.

Question 15

Spell the harmonic series in number intervals from the fundamental 1.

Answer 15

1 1 5 - 1 3 5 b7 - 1 2 3 #4 5 6 b7 7 1

Question 16

How is timbre distiguished among different instruments?

Answer 16

Differences in the intensity between prominent harmonics give each instrument its unique timbre.

Question 17

What role do synthesizers play in emulating the tone colors of various instruments?

Answer 17

Synthesizers emulate the tone colors of various instruments by manipulating the different harmonics.

Question 18

How do waveforms in electronic circuits provide control and timing signals for many applications?

Answer 18

In electronic circuits, these waveforms provide control and timing signals for many applications.

Question 19

Which harmonics are out of tune in the harmonic series?

Answer 19

The 7th (b7), 11th (#4),
and 14th (b7)

Question 20

Explain the difference in sound between a major third interval between C4 and E4 and the same interval pitched two octaves lower, C2 to E2.

Answer 20

The lower interval has more audible dissonant harmonics, resulting in a more dissonant and generally unpleasing sound often described as ‘muddy.’

Question 21

Define lower interval limits in the context of music.

Answer 21

Lower interval limits refer to the phenomenon where lower intervals have a greater density of dissonant harmonics in an audible register, causing almost all intervals to become more dissonant as the register gets lower.

Question 22

How is phase important in sound engineering?

Answer 22

Phase can measure how far in degrees a sound wave has traveled in its cycle at a given point, starting at 0° and ending one complete cycle at 360°.

Question 23

What is the relationship between two similar waves called?

Answer 23

Also “phase,” describing two sound waves either beginning and ending their cycles together–“in phase,” or not–“out of phase.”

Question 24

Explain the impact of register on the dissonance of intervals.

Answer 24

Lower registers result in intervals becoming more dissonant due to a greater density of dissonant harmonics that sound in an audible range.

Question 25

What is resonance and how does it occur in musical instruments?

Answer 25

Resonance is the transfer of vibrations from one source to another object. In musical instruments, sound is transferred from the source (e.g., guitar string) to the body of the instrument, causing the body to resonate at the same frequency as the source.

Question 26

Define reflection in the context of sound waves.

Answer 26

Reflection occurs when a sound wave collides with an object, loses some amplitude due to absorption, and then continues in a new direction after being reflected.

Question 27

How would you explain reverberation and its impact on sound perception in large enclosed spaces?

Answer 27

Reverberation refers to the continued reflection of sounds in a space after the source has stopped transmitting. In large enclosed spaces, such as cathedrals, reverberations can last several seconds due to the multiple reflections of sound waves.

Question 28

What are early reflections in the context of sound perception?

Answer 28

Early reflections are the sounds that arrive after the direct sound, having taken a longer path and been attenuated by reflection and extra distance.

Question 29

Define standing waves and their characteristics.

Answer 29

Standing waves are waves that are confined within a medium and vibrate at specific frequencies, creating nodes and anti-nodes. They can only form where whole wavelengths are possible, such as in the case of a guitar string.

Question 30

How do standing waves inside wind instruments create harmonics?

Answer 30

The total length of the air column inside wind instruments represents the fundamental, and the harmonics are created by dividing the total length into halves, thirds, etc., each producing nodes and anti-nodes.

Question 31

Describe the difference in the formation of standing waves in woodwind and brass instruments compared to a guitar string.

Answer 31

Woodwind and brass instruments create standing waves based on the shape of the instrument, with open ends that create different characteristic harmonics and an anti-node on one side of the air column.

Question 32

How are standing waves in a room similar to a fixed string?

Answer 32

The three-dimensional space of a room with standing waves is much more complex than a single fixed string, but the principle is the same.

Question 33

Define fundamental frequency in the context of sound waves in an enclosed space.

Answer 33

In an enclosed space, air serves as the medium for sound waves and has a fundamental frequency, similar to a guitar string.

Question 34

What impact do standing waves have on the perception of sound in a room or studio?

Answer 34

Frequencies are falsely reinforced or deadened by the acoustics of the room, particularly affecting low-end frequencies and requiring adjustment by sound engineers and players.

Question 35

Describe the impact of room size and internal structures on standing waves in concert halls and auditoriums.

Answer 35

Concert halls and auditoriums can also have standing waves, but due to their size and internal structures, the resonant frequency of the space is very low.