# EDAU 115 Exam 2 Study Guide

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## Description and Tags

Based on Assignment 1, the study guide, and items on the slides.

### 61 Terms

1

sound

the transfer of energy through an elastic medium

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2

What are the three necessary components for sound to occur?

1. energy - ex: lungs

2. a body capable of vibration - ex: vocal folds

3. transmitting medium - ex: air

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3

What are the physical properties of a sound source and transmitting medium?

1. the source must be able to vibrate; vibration requires mass and elasticity

2. the medium must be capable of being set into vibration; it also requires mass and elasticity

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4

mass

the amount of of matter present

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5

weight

gravitational force on an object

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mass vs weight

our mass is the same on Earth and on the moon, but our weight would be different ex: A 110 lb person on Earth would be 18 lbs on the moon, but the mass would be the same regardless where they are

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density

the amount of mass per unit volume

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8

elasticity

the property that enables recovery from distortion of shape or volume ex: air

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9

pressure

the amount of force per unit area ex: atmospheric pressure is 14.7 lb / inÂ˛

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10

Why arenât we able to hear sound in space?

There are too few particles, meaning there is nowhere for sound to go or any air molecules to bump into

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11

simple harmonic motion

the swaying back and forth motion of molecules or a disturbance in a medium in which particles are disturbed perpendicular to the direction of disturbance; also known as sinusoidal motion

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12

condensation

when simple harmonic motion occurs, particles in a medium are pushed together

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13

rarefaction

when simple harmonic motion occurs, particles in a medium are pulled apart

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14

What are the 5 measurements of a sine wave?

1. amplitude

2. frequency

3. period

4. phase

5. wavelength

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15

amplitude

perceptually equates to loudness; maximal displacement of particles in a medium

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16

rms amplitude

average amplitude of the waveform over time (rms = 0.707 x peak amplitude); used to measure the amplitude/intensity of a voice

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17

frequency

number of complete cycles per second (Hz); pitch = the perceptual correlation of frequency; pitch associated with human voice = F0 ex: 250 Hz higher perceived pitch than 100 Hz

f= 1/T

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18

cycle

a complete repetition of the oscillation

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19

simple sounds

single frequency (pure tone ex: tuning fork); not commonly found in nature and has no change in frequency; useful for tests and measurements

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20

complex sounds

sounds containing more than 1 frequency (speech)

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21

period

time that it takes for a vibrating object to complete one cycle of vibration

T = 1/f

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phase

represents the point in the cycle at which the vibrating object is located at a given instant in time

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in-phase

two sinusoids are in phase when their wave disturbances crest and trough at the same time

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out-of-phase

sine waves (180Â°) are out of phase when they are out of sync, and thus create a cancellation effect; commonly used for active noise reduction systems ex: headphones

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wavelength

distance that a sound wave travels during one complete cycle of vibration

Îť=s/f - measured in meters (f in Hz and speed = 340 m/sec)

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frequency vs wavelength

they have an inverse relationship; low frequency = longer wavelength, high frequency = shorter wavelength

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27

decibel

unit used for measuring the amplitude/intensity (loudness) of sound; we use decibels because it makes our numbers easier to work with and interpret

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28

peak clipping

Peaks of the waveform are cut off due to amplifier circuits being overdriven

Solutions: dynamic compression and limiting â> makes sounds more consistent

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29

transverse wave

the medium is displaced perpendicular to the direction of the traveling wave ex: light

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longitudinal wave

the medium is displaced parallel with the direction of the traveling wave ex: sound

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speed of sound

depends on 2 properties: 1. stiffness 2. density

high speed of sound depends more on the stiffness of dense materials

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imperial system

foot, pound, second (fps)

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metric system

meter, kilogram, second (mks); centimeter, gram, second (cgs)

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34

band pass filter

signals that only allow certain frequencies through the system; reason why voice sounds thin + raspy over the phone

300-3,400 Hz band pass filter - sounds most important for speech

Note: digital systems like Face Time are not tied down by band pass, which is why FT is crisper since not much filtering is occurring

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35

fundamental frequency

the lowest rate of vocal fold vibration (F0, first harmonic); associated with pitch - smaller/shorter vocal folds will vibrate at a higher frequency than larger/longer vocal folds (the reason why children have higher-pitched voices)

F0 of adults = 80-300 Hz

F0 of children = 200-500 Hz

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36

harmonics

an integer multiple of the fundamental frequency

ex: F0 = 100 Hz, 2nd harmonic =200 Hz, 3rd= 300 HZ, 4th= 400Hz

F0 = 150 Hz, 2nd= 300 Hz, 3rd = 450 Hz

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37

Which harmonics make up formants necessary for vowel discrimination?

3rd and 5th harmonics

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38

formants

created by the resonance of sound transmitted through the vocal tract

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39

What is the relationship between vocal tract length and formant frequencies?

formants have an inverse relationship with vocal tract length

ex: longer vocal tract = lower frequency formant values; shorter vocal tract length = higher frequency formant values

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40

Which tongue positions affect F1 and F2?

F1 is determined by the tongue height (the higher the tongue is, the lower the frequency); F2 is determined by the back-ness/forwardness (the further forward the tongue, the higher the frequency)

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F3

related to vocal tract length

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acoustic resonance

an object or a system vibrates at a specific natural frequency when exposed to an external sound wave or vibration; all objects have a frequency at which they vibrate best at

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cavities/spaces

generally have lower resonant frequencies, smaller cavities have higher resonant frequencies (based on particle velocity and wavelength)

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44

categorical perception

the psychoacoustic phenomenon where sounds are generally perceived as distinct categories; perception changes rapidly when some acoustic attribute (ex: VOT) is varied

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45

source filter theory

describes acoustic output during speech-sound production; comprised of:

1. source - voiced or voiceless signal

2. filter ex: vocal tract

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voice onset time

refers to the duration between the release of a plosive/stop sound and the beginning of vocal fold vibration; voiceless consonants have longer VOT than voiced consonants

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long term average spectrum (LTAS)

describes the frequency (pitch) distribution of energy for speech produced over a brief period of time (1-2 minutes); decreases in amplitude at about -6 dB/octave

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male vs female LTAS

• LTAS for male speakers contains more energy below 1000 Hz

• female voices have increased high-frequency energy

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49

What are the 3 factors used to classify consonants?

1. place - location of airflow restriction in the oral cavity during speech production

2. manner - how sound is produced

3. voicing - presence or absence of vocal fold vibration

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50

Ling 6 speech sounds test

sound test that is a set of 6 speech sounds: /É, i, u, Ę, s, m/

each sound represents a frequency region (low, mid, high)

commonly used as a daily biologic check to confirm amplification device function (hearing aids)

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continuous signal

a signal that has a value at any given time

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discrete signal

a signal produced by sampling amplitude at a given rate

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53

amplitude quantization

capturing the amplitude of the continuous signal, more bits = more lvls of amplitude

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What does a high bit rate wave look vs. a low bit rate wave?

most current digital systems use 16- or 24-bit, as these values provide for sufficient and high-quality reproduction of continuous signals for most auditory applications

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sampling frequency/rate

refers to the number of amplitude samples taken (i.e. sampled points) in a given period of time, typically one second

commercially available audio and speech processing systems, ranging from 8kHz to over 300 kHz

ex: sampling freq. of 16 kHz means that amplitude values are obtained 16,000 times each second

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56

Nyquist Theorem

states that the sampling frequency required for a given application must be at least twice that of the highest frequency of interest in the output signal (at least two samples per cycle are required)

ex: for 20 kHz, sample rate would be 40 kHz

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According to the Nyquist Theorem, what is the minimum sampling rate required to accurately digitize a 20,000 Hz sine wave?

40 kHz (20,000 Hz = 20 kHz), so 20kHz x2

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aliasing

occurs when a signal is sampled at a frequency that is insufficient for the application; distortion that occurs when reconstructed digital signal is different from the original signal - occurs when Nyquist Theorem has been violated

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59

auditory recruitment

when quiet sounds become inaudible and loud sounds become uncomfortable; result of sensory hearing loss (cochlear outer hair cell damage) leads a reduced dynamic range and abnormal growth of loudness

solution: hearing aids, can help amplify sounds and compressor helps with maintaining lvls of sound

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60

How does stiffness and density of a medium affect the speed of sound?

greater stiffness of a medium will result in greater speed â> determines speed better than density, but less density of the medium will result in greater speed

ex: sound is faster in water than in air due to the greater stiffness of water

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61

Label the axis of the spectrogram of the vowel sound /i/ using the following values: F1, F2, F3

F1 250 Hz, F2 2,200 Hz, F3 2,800 Hz

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