Acoustics

Question 1

sound waves

Answer 1

travelling pressure fluctuations that propagate through a medium (air, water)

Question 2

pressure fluctuations

Answer 2

caused by pushing and pulling of air molecules

pressure in a particular spot (e.g., just oustide your eardrum) fluctuates over time, with peaks of rarefaction and compression

Question 3

sine wave

Answer 3

a simple S-shaped periodic wave

Question 4

y-axis

Answer 4

amplitude of the wave (distance between the resting position and the crest of a wave)

intensity of the wave (its distance distance from 0, describes the energy of the wave in decibels)

Question 5

x axis

Answer 5

frequency (the number of cycles in a certain period of time - the frequency with which the pattern repeats)

frequency indicates time, often in milliseconds

Hz = cycles/sec = 25/1s = 1/0.04s = 25Hz
Hz = cycles/sec = 125/1s = 1/0.008s = 125Hz

Question 6

pitch

Answer 6

correlated with frequency (the greater the frequency, the higher the pitch)

Question 7

periodic wave

Answer 7

wave that has a regular, repetitive pattern

Question 8

complex periodic waves

Answer 8

sound waves associated with vowels and voiced sonorants (can be split into combinations of simple sine waves)

Question 9

aperiodic waves (noise)

Answer 9

waves that display random fluctuations of intensity and result from random turbulence in the airstream (fricatives)

many sounds are a combination of periodic and aperiodic waves

Question 10

harmonics

Answer 10

individual component waves

gradually decrease in intensity at higher frequencies

are shaped by the resonant properties of the vocal tract

Question 11

fundamental frequency (f⁰)

Answer 11

the harmonic with the lowest frequency

the frequency of the complex wave as a whole is the same as the frequency of the fundamental

all of the harmonics above the fundamental have a frequency that is a multiple of the fundamental (if f⁰ = 100Hz, then H2 = 200 Hz, H3 = 300Hz)

the distance between H1 and H2, and between H2 and H3 is equal to f⁰ (if you know the frequency of H10, you can divide by 10 to find f⁰)

Question 12

resonance

Answer 12

the natural dentency of a body to vibrate at certain frequencies, and this depends on the shape of the vibrating object and resonant chambers

Question 13

formants

Answer 13

clusters of harmonics that are reinforced by the shape of the vocal tract

Question 14

oscillogram

Answer 14

waveforms that represent intensity on the y axis (sine waves)

Question 15

spectrum (spectra)

Answer 15

display a slice at a single moment in time (spectral slice)

represent amplitude on the y axis and frequency on the x axis

Question 16

spectrogtam

Answer 16

has 3 dimensions:
x-axis (time)
y-axis (frequency)
darkness (intensity)

Question 17

wide-band spectrogram

Answer 17

vertical striations = glottal pulses

better temporal resolution; easier to see formants (the dark horizontal bands)

Question 18

narrow-band spectrogram

Answer 18

horizontal striations = harmonics

better frequency resolution; easier to see individual harmonics; can use it determine f⁰ (count up 10 harmonics and divide the frequency by 10)