EDAU 115 Exam 2 Study Guide

the transfer of energy through an elastic medium

1. energy - ex: lungs

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

3. transmitting medium - ex: air

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

the amount of of matter present

gravitational force on an object

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

the amount of mass per unit volume

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

the amount of force per unit area ex: atmospheric pressure is 14.7 lb / in²

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

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

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

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

1. amplitude

2. frequency

3. period

4. phase

5. wavelength

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

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

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

a complete repetition of the oscillation

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

sounds containing more than 1 frequency (speech)

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

T = 1/f

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

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

sine waves (180°) 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

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

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

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

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

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

Solutions: dynamic compression and limiting —> makes sounds more consistent

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

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

depends on 2 properties: 1. stiffness 2. density

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

foot, pound, second (fps)

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

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

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

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

3rd and 5th harmonics

created by the resonance of sound transmitted through the vocal tract

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

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)

related to vocal tract length

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

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

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

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

1. source - voiced or voiceless signal

2. filter ex: vocal tract

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

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

• LTAS for male speakers contains more energy below 1000 Hz

• female voices have increased high-frequency energy

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

sound test that is a set of 6 speech sounds: /ɑ, i, u, ʃ, 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)

a signal that has a value at any given time

a signal produced by sampling amplitude at a given rate

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

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

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

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

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

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

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

greater stiffness of a medium will result in greater speed —> 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

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