Exam 4

Question 1

What is a spherical wave?

Answer 1

A wave that radiates outward in all directions from a point source

Question 2

What is a plane wave?

Answer 2

A wave that travels in one direction with parallel wavefronts

Question 3

What does the inverse square law state?

Answer 3

Explains the decrease in sound intensity over distance

Question 4

How is the inverse square law related to distance?

Answer 4

Doubling the distance from the source decreases intensity by factor of four

Question 5

What are “interest distance” and “reference distance”?

Answer 5

Used to calculate change in sound intensity at different points using the inverse square law

Question 6

What happens when sound is absorbed?

Answer 6

Sound penetrates the obstacle

Question 7

What is sound reflection?

Answer 7

When sound bounces off a surface.

Question 8

What are incident and reflected waves?

Answer 8

Incident = original wave hitting a surface
Reflected = wave bouncing back

Question 9

How do concave surfaces affect sound?

Answer 9

They focus sound waves to a point

Question 10

How do convex surfaces affect sound?

Answer 10

They scatter or disperse sound waves

Question 11

What is reverberation?

Answer 11

The persistence of sound due to multiple reflections

Question 12

What is RT60?

Answer 12

The time it takes for sound to decay by 60 dB in a room

Question 13

What causes standing waves?

Answer 13

The interaction between incident and reflected waves, creating nodes and antinodes

Question 14

What is a 1/4 wave resonator?

Answer 14

A tube closed at one end (e.g., ear canal); supports odd harmonics only

Question 15

What is a 1/2 wavelength resonator?

Answer 15

A tube open at both ends; supports both even and odd harmonics

Question 16

What is constructive interference?

Answer 16

When waves combine to make a louder sound (in-phase).

Question 17

What is destructive interference?

Answer 17

When waves cancel each other out (out-of-phase).

Question 18

What determines formants in the vocal tract?

Answer 18

Vocal tract length and the odd harmonics of a 1/4 wavelength resonator

Question 19

What is refraction in sound?

Answer 19

Bending of sound waves due to changes on medium (e.g. temperature, wind)

Question 20

What is diffraction?

Answer 20

Bending of sound around obstacles, especially low frequencies

Question 21

Why do low frequencies diffract more?

Answer 21

They have longer wavelengths

Question 22

What is sound localization?

Answer 22

They ability to identify the direction of a sound source

Question 23

What are beats in acoustics?

Answer 23

Pulsing sound from interference between two close frequencies

Question 24

What is the Doppler Effect?

Answer 24

Change in pitch due to movement of sound source or listener

Question 25

What causes a sonic boom?

Answer 25

An object moving faster than the speed of sound creates a shockwave.

Question 26

What effect does absorption have on sound?

Answer 26

Reduces intensity reflected sound, and reverberation time

Question 27

What type of materials absorb sound the best?

Answer 27

Soft, porous materials like foam or fabric.

Question 28

What is a "live" room?

Answer 28

A room with lots of reflection and long reverberation time

Question 29

What is a "dead" room?

Answer 29

A room with sound-absorbing materials and minimal reflections

Question 30

What is an anechoic chamber?

Answer 30

A room with no reflections at all

Question 31

How does room volume affect reverberation?

Answer 31

Larger rooms have longer reverberation times

Question 32

What is sound isolation?

Answer 32

Preventing sound from entering or leaving a space

Question 33

What is the sampling rate in digital audio?

Answer 33

How often audio is measured per second

Question 34

What is the Nyquist frequency?

Answer 34

Half the sampling rate; highest frequency that can be accurately recorded

Question 35

What is aliasing?

Answer 35

Distortion caused by sampling below the Nyquist rate

Question 36

What are the main parts of a microphone?

Answer 36

Diaphragm, coil, magnet, and battery (in condenser mics).

Question 37

What are the parts of a loudspeaker?

Answer 37

Woofer (low), midrange driver (mid), tweeter (high).

Question 38

What is the Mel scale?

Answer 38

A scale of perceived pitch based on how humans hear.

Question 39

What are phons?

Answer 39

A unit of loudness based on equal-loudness contours

Question 40

What are sones?

Answer 40

A linear scale of loudness (e.g., 2 sones = twice as loud as 1 sone).