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?