Week 1 - Acoustics Flashcards

1
Q

Sound waves

A

compressions and rarefactions of air molecules

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2
Q

Compressions

A

Regions of increased density

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3
Q

Rarefactions

A

Regions of decreased density; restorative force and momentum

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4
Q

Waveform

A

Graphical display that represents the alternating compressions and rarefactions of air molecules that make up the longitudinal sound pressure wave

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5
Q

Airborn sound waves

A

Generated by a mechanical source - rapid vibration in air pressure

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6
Q

Periodic waves

A

Regular, repeating pattern of compression and rarefaction

Sound source is vibrating at a regular rate (F0)

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7
Q

Aperiodic waves

A

Mechanical source without regular/oscillating movement

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8
Q

Simple waves

A

Pure tones, sine waves
Consists of one tone
Not naturally occuring

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9
Q

Complex sound waves

A

More than one frequency
Either aperiodic/periodic
Combination of sine waves, each with own frequency, amplitude and phase

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10
Q

Frequency

A
Number of oscillations in a second
Measured in hertz 
Can hear 20-20 000Hz
Less cycles/sec = lower Hz, lower pitch
High cycles/sec = higher H, high pitch
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11
Q

Air pressure

A

Amount of change in air pressure from sound
Relates to vertical height of waveform
Measured in Pascals, Dynes/cm^2

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12
Q

Decibel scale

A

Sound pressure and intensity simplified into 140 units

0-140dB threshold of hearing

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13
Q

Conversation - dB

A

60dB

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14
Q

Pain threshold - dB

A

130-140dB

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15
Q

Period

A

Amount of time taken to complete one cycle

Can measure duration of vowels, words, pauses during connected speech

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16
Q

Velocity

A

Speed at which the sound wave travels through a medium

wavelength = velocity/frequency

17
Q

phase

A

Starting point of one cycle of tone/frequency

18
Q

Wave length

A

distance travelled by one cycle of the waveform

wavelength = velocity/frequency

19
Q

Decibel Scale

A

shows how loud a sound is relative to the threshold of hearing
Can be measured according to sound pressure level (SPL)/sound intensity (SI)
Consists of 140 points

20
Q

Fundamental frequency

A

Main, lowest oscillation frequency of mechanical source

21
Q

Harmonic Spectrum

A

Multiples of the fundamental

Consists of the F0 and higher harmonic frequencies

22
Q

Vowel features - frequency

A

Periodic, therefore have periodic soundwave features;

F0 and harmonic frequencies

23
Q

Pitch

A

Psychological correlate of F0

24
Q

Loudness

A

Psychological correlate of amplitude

25
Timbre/quality
Psychological correlate of sound complexity
26
Psychophysical scaling
quantifies psychological dimensions of the physical properties of sound
27
Sone
Psychological scale of loudness
28
Mel
Psychological scale of pitch
29
Spectral Analysis
Analyses of the simple sine wave components making up complex sound Spectrum = freq, amplitude, phase
30
Spectral Analysis - periodic vs aperiodic
Periodic - evenly spaced peaks | Aperiodic - no peaks
31
Pitch Analysis Methods
Cross Correlation | Autocorrelation
32
Problems with analysis
provide highly inaccurate estimates of F0; due to background noise, disordered voice, inappropriate set up for pitch analysis
33
Psychological correlates - frequency
pitch
34
Psychological correlates - amplitude
loudness
35
Psychological correlates - complexity
quality/timbre | depends on harmonic content, dynamic characteristics