Acoustics 1

Question 1

What is the definition of frequency

Answer 1

The number of oscillations in a given unit of time (e.g. 1 second), measured in Hertz (Hz)

Question 2

What is the definition of Fundamental Frequency?

Answer 2

The lowest frequency of a periodic waveform

Question 3

What is the definition of a periodic sound?

Answer 3

A sound wave that has regular or repeating patterns of compression and rarefaction due to the oscillation of the mechanical sound source

Question 4

What is the definition of an aperiodic sound?

Answer 4

A sound wave produced by mechanical sources that have no regular oscillating movement, and thus having no pitch

Question 5

What is a complex sound wave?

Answer 5

Sound waves that have more than 1 frequency (can be periodic or aperiodic) → can be viewed as a combination of simple sine waves → can be periodic or aperiodic

Question 6

What is a simple sound wave?

Answer 6

Periodic waveforms that consist of only 1 frequency (aka sine waves/ pure tones) → never naturally occuring

Question 7

What is the definition of wavelength?

Answer 7

The distance travelled by one cycle of the waveform

Question 8

What is the definition of phase?

Answer 8

Relative timing or position of a sound wave at a given point in time → usually the starting tone of a waveform with respect to the next tone

Question 9

What is the definition of amplitude?

Answer 9

The amount of change in air pressure produced by a sound source (aka the amount of displacement of air particles from their point of equilibrium)

Question 10

What is Pascals?

Answer 10

The unit of measurement for air pressure that denotes force per unit area

Question 11

What is dB SPL?

Answer 11

a relative measure of sound pressure level with respect to a reference (e.g. human hearing range)

Question 12

What is dB IL?

Answer 12

a relative measure of sound intensity level with respect to a reference (e.g. human hearing range)

Question 13

What is spectral analysis?

Answer 13

An analysis that decomposes any sound wave into its simple sinusoidal components

Question 14

What are harmonics?

Answer 14

A harmonic is a wave or signal whose frequency is an integral (whole number) multiple of the frequency of the same reference signal or wave

Question 15

What is pitch?

Answer 15

The psychological correlate of the fundamental frequency of a periodic sound wave

Question 16

What is loudness?

Answer 16

The psychological correlate of amplitude

Question 17

What is sone?

Answer 17

A unit used to measure the psychological scale for loudness

Question 18

What is mels?

Answer 18

A unit used to measure the psychological scale for pitch

Question 19

What is the range of sound intensities humans can usually hear?

Answer 19

0 dB to 120 dB

Question 20

Identify common dB levels of sounds.

Answer 20

Whisper (30dB), screaming (90dB/ threshold for endangering hearing), concert (120dB/ threshold for pain), and jet engine (150dB/ total deafness may occur)

Question 21

Identify the range of sound frequencies humans can normally hear.

Answer 21

20 Hz to 20,000 Hz

Question 22

Identify the range of frequencies associated with human speech.

Answer 22

85 to 155 Hz for males and 165 to 255 Hz for females

Question 23

Compare the physical scales for sound intensity and frequency with their respective psychological dimensions.

Answer 23

Sound intensity is known as amplitude (dB) and is the physical correlate of loudness (sone). Frequency (Hz) is the physical correlate of pitch (mels).

Question 24

Label the axes of a time amplitude waveform and a spectrum - including units.

Answer 24

For a time-amplitude waveform, the x-axis is amplitude (dB) and the y-axis is time (s). For a spectrum the x-axis is frequency (Hz) and the y-axis is amplitude (dB).

Question 25

Why are harmonic peaks evenly spaced from left to right across the frequency dimension?

Answer 25

Harmonics are integral multiples of the fundamental frequency of a soundwave, thus their peaks are evenly distributed.