Basic Elements Of Acoustics

Question 1

What is sound?

Answer 1

Repetitive changes in air pressure that propagates in waves

Question 2

What happens to particles that carry the sound wave?

Answer 2

The particles oscillate back and forth but do not propagate with the wave signal (e.g., think of a wave in a stadium). Particles remain around a fixed point.

Question 3

What are the 3 characteristics of sound?

Answer 3

Amplitude (loudness)
Wavelength
Frequency (pitch)

Question 4

What is amplitude measured in?

Answer 4

dB (decibels)

Question 5

What is the human hearing threshold?

Answer 5

0 dB

Question 6

What is wavelength?

Answer 6

Distance between peaks

Question 7

What does frequency measure?

Answer 7

Cycles per second (Hz)

Question 8

What range of frequencies are humans sensitive to?

Answer 8

20-20,000 Hz

Question 9

What does a higher frequency indicate?

Answer 9

Higher pitch

Question 10

What does a larger amplitude indicate?

Answer 10

Louder sound

Question 11

What does a short wavelength refer to?

Answer 11

High frequency

Question 12

What does large wavelength refer to?

Answer 12

Low pitch sounds

Question 13

What is measured in dB?

Answer 13

Sound pressure (amplitude)

Question 14

Are most sounds pure sine waves?

Answer 14

No. Most sounds are complex sounds.

Question 15

Who is Fourier?

Answer 15

Mathematician

Question 16

What did Fourier say about waveforms?

Answer 16

Every periodic waveform is composed of harmonically related sinusoids with unique amplitudes

Question 17

What is the fundamental frequency?

Answer 17

The musical pitch of a note that is perceived as the lowest

The lowest frequency sinusoidal in the sum

Question 18

What are abbreviations of the fundamental frequency?

Answer 18

fo

FF

Question 19

How do our ears identify the fundamental frequency?

Answer 19

Our ears identify the FF as the specific pitch of the musical tone (the individual frequencies are blended together by our ear/brain into a single tone)

The FF is the loudest frequency

Question 20

What are most natural sounds made up of?

Answer 20

One fundamental frequency

Several harmonics of the fundamental frequency - waves of the frequency that is a positive integer multiple of the fundamental frequency

Additional frequencies

Question 21

What does Fourier analysis of a waveform show us?

Answer 21

Can see the distribution of the frequencies from which the waveform is made of

Can see the decomposition of the wave

Question 22

What is a sound a mix of?

Answer 22

A mix of fundamental and different additional frequencies

Question 23

Describe the amplitude of additional frequencies

Answer 23

Lower amplitudes than the FF, thus they are not as loud

Question 24

Will violin and piano produce same or different waveforms?

Answer 24

Different waveforms

Question 25

What can the FF be decomposed into?

Answer 25

Several simple sine waves

Question 26

Will violin and piano have the same or different FF?

Answer 26

Same FF (220 Hz)

Question 27

What is timbre related to?

Answer 27

Related to the harmonic structure of a tone

Question 28

Why might tones of the same loudness, pitch, and duration sound different?

Answer 28

Different timbre

Question 29

What is the Power Spectrum of a signal?

Answer 29

The representation of sounds by the intensities (dB) of their simple sound waves The presentation of the distribution of frequencies