Speech Science: Acoustics (study guide)

noise

aperiodic movements (unpredictable sounds)

phase

any moment in a cycle may be expressed as this

sound pressure level (SPL)

(what happens in air); perhaps the most common measure use in speech pathology; represents the energy in terms of the energy of pressure waves associated with sound as measured at some point away from the sound source

potential, kinetic

_______ energy changes into _______ energy when you let go of the swing and it starts moving again

pure tones

an audible vibration in air that contains one, and only one, frequency of vibration

free vibration

an object is of a nature that permits it to vibrate freely; takes on its own natural resonant frequency

phons

are lines of "perceived equal intensity" across the audible frequency domain. They represnt the "audiogram of the human species" the different hearing thresholds as they exist at different frequencies when measured among a large number of people with "normal hearing"

complex sound

consists of multiple frequencies

cps

cycles per second

mels

determined through the so-called "scaling method" (subjects are instructed to move the setting of a dial proportionately to the experienced pitch levels; the perceptual scale of frequency is expressed in this; unit of measurement for the subjective pitch scale

simple sound

ex: of this is a pure tone; only contains one frequency

weber fechner law

explains sound intensity; in other words, our hearing system is extremely sensitive at the low end of sound intensity, and extremely insensitive for detecting difference at the high end of sound intensity

power spectrum

graphic representation of frequency (x) and sound intensity (y)

anechoid chamber

has no echo; is a room that is treated to not reflect sound from walls in any possible way, and that is insulated against any outside noise or vibration; used for ex: in research of our sense for the direction of sounds

they are both independent variables

how are frequency and amplitude related?

through comparing perceived intensities across difference frequencies

how are phons determined?

the db level lines of an audiogram reflect the phons rather than actual differences in sound intensity

how are phons related to audiograms?

frequency

how close the waves are together (how fast it is); vibration rate measured in cycles per second

it is in a continuous state of change

how does velocity change throughout a cycle?

same, in, same, identical, twice

if two signals of the ____ frequencies are __ phase their pressure waves crest and trough at the ____ time and if their amplitudes are ______ the sum of the signals has ____ the amplitude of each component signal

decibels

makes the measuring unit of bels more precise;s a logarithmic unit used to express the ratio between two values of a physical quantity, often power or intensity. One of these quantities is often a reference value, and in this case this can be used to express the absolute level of the physical quantity, as in the case of sound pressure.

rarefaction

negative pressure wave

continuous spectrum

one type of power spectra; best solution

old fashioned

one type of power spectra; discrete system; creates blocks/bars to describe what a general region does

longitudinal waves

oscillates in the same direction as the direction of which it spreads, like a slinky

transverse waves

oscillates perpendicularly to the direction to which it travels

pitch

perceptual, how high or low the sound it

compression

positive pressure wave

periodic vibration

predictable patterns of vibrations or harmonic vibrations

simple harmonic motion

pressure wave forms creating plus or minus pressure; each molecules doing the same thing and following the sound source; pure tone= sine wave

sound intensity (IL)

reflects the amount of physical energy that is employed by some device to produce the intensity. Entirely a physical measure; it you want to measure it, it is usually done electronically, but it could conceivably also be based on physical measures of vibration at the source (not in air)

just noticeable difference (jnd)

relevant for intensity, pitch; how high can we go before we notice a change in sound`

sound

represents a complex mixture of vibrations in the air that surround a listener

reverberation

sum of all echos in a room large enough

wave length

the distance a sound travels while completing one cycle.

period

the duration of a cycle is this

natural resonant frequency

the frequency at which a system vibrates with greatest amplitude when driven by an external vibrating source

loudness (HL)

the most subjective equivalent form of measuring sound intensity; adjustments are made for typical differences in hearing sensitivity at different frequencies. This scale, at the perceptual level, would lead to the most accurate results and therefore is the measure used in hearing evaluations

cycle

the repeated element (shape) is called this

bels

the unit of a sound intensity scale; a unit for comparing two power levels, equal to the logarithm to the base ten of the ratio of the two powers.

forced vibration

this type of vibration may briefly exist, but soon dampen as they loose their energy to the environment more quickly

sound propagation

traveling of sound; sound goes through the air as a longitudinal wave

results of the fourier analysis

two separate lists of numbers that describe the frequency components of a signal. one list contains the individual frequencies that were detected, while the second column specifies their respective individual intensities. These numeric results may be used to produce graphical representations, called power spectra

aperiodic vibration

unpredictable vibrations; without any distinguishable pattern

ultra-sonic

vibrations too high in frequency to be audible ex: bats and insects; have a clearly defined direction, but loose their energy to the environment very quickly

sub sonic (infra sound)

vibrations too low in frequency to be audible ex: elephants and other large mammals; these sounds are known to travel large distances, and through irregular terrain; it works itself through obstacles

formants

vocal tract resonances

200-260 hz

what are the fundamental frequencies for females?

100-120 hz

what are the fundamental freuqencies for males?

500-2,000 hz (80-8,000 hz)

what are the speech frequencies?

the resulting sound signal does not have the appearance of individual sine waves anymore

what happens if enough frequencies are mixed?

silence

what happens if two sounds are 180 degrees out of phase?

1 signal is 1/4 of a cycle ahead of the other

what happens if two sounds are 90 degrees out of phase?

inertia (acceleration) cause the swing to move back up in the opposite direction

what happens when the velocity is maximal?

20-20,000 hz (16-20,000 hz)

what is the audible frequency range?

is the convenience in calculating the acoustic resonance of cavities

what is the purpose of using the concept of wavelength for sound?

greatest at the bottom of a cycle

when is velocity the greatest in a cycle?