Exam 2 Flashcards
Frequency
- Rate of vibration of an object
- # of cycles occurring in an amount of time
- Unit: Hertz (Hz; cycles/second)
Period
- Amount of time it takes for one cycle in a wave to complete
- Unit: s, ms
Euqations for Frequency/Period
Reciprocal relationship/inverse; you can find one if you have the other.
Periodic sounds
- Sounds with a regular, repeating pattern
- each cycle takes the same time to occur (period)
- pressure changes (amplitude) are equal for all cycles
Aperiodic sounds
No regular, repeating pattern
- cycles do not take the same amount of time to ocur
- sounds like noise
Waveform
A graph with time on the horizontal (X) axis and amplitude on the vertical (Y) axis. Shows…
- movement over time
- increases/decreases in air pressure
Wavelength
The distance it takes for one cycle to occur.
Equation for wavelength
Inverse relationship between wavelength and frequency (higher frequency = shorter duration of period = shorter wavelength)
- v = speed of sound; stays constant as long as you don’t change the medium
Incedent wave
A sound wave that is generated, travels a certain distance, and then hits up against a boundary.
Boundary behaviors: transmission
Sound passes through the boundary
Boundary behaviors: Absorption
Damping of a wave with diminishing changes in air pressure due to friction.
Boundary behaviors: reflection
Some portion of the sound that is not transmitted or absorbed bounces back from the surface of the boundary and travels in the opposite direction of the incident wave at the same speed.
Boundary behaviors: diffraction
Sound bends around an obstacle without going through the boundary.
Boundary behaviors: refraction
Sound bounces back from the surface of a boundary in a different direction, speed & angle.
Interference
Occurs when 2 or more waves combine with each other in terms of areas of high and low pressure.
Constructive interference
Waves combine, reinforce each other, and increase the resultant amplitude
- sounds are in phase
Deconstructive interference
Waves combine and decrease the resultant amplitude
- sounds are out of phase
Complex interference
Effect depends on the degree to which the two waves are in or out of phase
(pic: some areas of decreased/increased amplitude)
Reverberation
Generates a sound that lasts slightly longer due to the interaction of intecedent and reflected waves
Simple Harmonic Motion (SHM)
A smooth back and forth movement with a characteristic pattern of acceleration through the rest position and deceleration at the endpoints of movement.
- generates a pure tone
Pure tone
A sound wave that has only one frequency
- generated by an object vibrating in SHM (Ex: tuning fork)
Complex sound
A wave consisting of two or more frequencies
Two types: periodic & aperiodic
Complex periodic sounds
Consist of a series of frequencies that are systematically related to one another.
- lowest frequency is fundamental frequency (F0), or first harmonic
- multiples of F0 are harmonic frequencies
Fourier analysis
Mathematical procedure to identify the individual sinusoids in a complex sound.
- plots amplitude (Y axis) vs. frequency (X axis)
Spectra
Graph with frequency on the X axis & amplitude on the Y axis (waveforms plot time, not frequency)
Line vs. continuous spectra
- Line spectra: frequency of periodic sounds
- Continuous spectra: frequency of aperiodic sounds
Continuous vs. Transient aperiodic sounds
- Continuous: white noise (constant)
- Transient: /k/, finger snap (not constant)
Perceptual correlates to physical measures of frequency & intensity
Mels vs. Hertz graph
- Mels on Y, Hz on X
- Related, but not in a linear matter
- We’re not that good at resolving frequency changes at higher frequencies
On what physical characteristics does frequency depend?
- Size (kids vs. adults)
- Length (flute vs. piccolo)
- Thickness
- Density
- Stiffness
- Tension
- Mass
*all apply to the vocal folds
Subsonic & Supersonic sounds
- Subsonic: < 20 Hz
- Supersonic > 20,000 Hz
What causes human perception of frequency?
Place of maximum excitation on the basilar membrane
Shepard scale
Ambiguous set of sounds that constantly sound like they’re ascending/descending.
Amplitude
Amount of displacement of air molecules from their rest position.
- cgs system: dynes per square centimeter (dyne/cm2)
- MKS system: micropascals (µPa)
Energy
The capacity of an object to perform work.
- Measured in ergs (cgs) or joules (MKS)
Work
A push/pull that moves an object a certain distance.
- You can expend energy but do no work
Power
The amount of energy expended in a given time.
- Measured in watts (W)
- Liesurely stroll vs. sprint
Intensity
Power (i.e., amt. of energy expended in a second) transferred over a particular area.
- Measured in watts per square cm (W/cm2)
Loudness
The psychological correlate of intensity
Amplitude-Intensity-Frequency Relationship (on ELCG)
Our ability to hear sounds depends on frequency. Curves represent equivalent loudness level.
- sounds from 1000-4000 Hz don’t have to be as loud for us to hear them
- a 100 Hz sound at 60 dB sounds as loud as a 1000 Hz sound at 50 dB
- bottom dotted line is minimum audibility curve
As distance increases by a factor, intensity…
decreases by the factor squared
- If you’re 2 units from someone, by the time the sound gets to them, it’ll be decreased by a factor of 4 (22 = 4)
If the amplitude of a sound is increased by a factor, the intensity of the sound will be….
increased by the factor squared
- if amplitude increases by 5, intensity will increase by 25 (52 = 25)
dB (IL)
Measure of intensity using power as a reference
- reference is 10-12 W/m2
- dB IL = 10(log W1/Wr)
dB (SPL)
Measure of speech volume using sound pressure
- Standard reference is 10-12 W/m2 or 20 µPa
- dB SPL = 20 (log10 P1/Pr)
Standard Reference Sound
The softest sound of a particular frequency that a pair of normal human ears can hear 50% of the time under ideal listening conditions. This is the threshold of hearing.
- Amplitude: 20 µPA or 0.0002 dyne/cm2
- Intensity: 10-12 W/m2
Threshold of Pain
Any frequency with an intensity of 130 dB or greater
Logarithmic scale
dB scale is one. Scales that contain units that increase by greater and greater amounts by you go up the scale.
- Cannot be added/subtracted because the units aren’t equal
Average f0 or SFF
The f0 measured in a particular task such as sustaining a vowel, reading aloud, or conversational speech, and averaged over the speaking time of the task.
- when measured in reading or conversational speech, this is referred to as speaking fundamental frequency (SFF)
Pitch sigma
Measure of frequency variability that measures the standard deviation around the average f0 in semitones.
- Should be 2 to 4 semitones
Frequency range
Measure of frequency variability. Difference between the highest and lowest f0 in a particular sample of speech.
- less meaningful than pitch sigma
Maximum phonational frequency range (MPFR)
The complete range of frequencies that an individual can generate
- from lowest to highest (falsetto)
- not used in everyday speech
Semitones
Smallest musical interval used in Western tonal music
- Relationship is not linear; the frequency difference in 2 notes is not the same even if they differ by the same # of ST
- One octave = 12 ST
Formula for finding the range of semitones b/w 2 frequencies
Formula for finding frequency increased by a # of semitones
To raise a semitone by one octave, you must ______ the frequency.
double
0 ST reference value
16.35 Hz
Average amplitude level
Indicator of how loud somebody is on average in dB SPL.
Amplitude variability
Standard deviation around average amplitude in dB SPL.
Dynamic range
Range of vocal amplitudes that a speaker can generate, from the softest phonation that is not a whisper to the loudest shout.
- should be around 30 dB SPL
Voice range profile
Also VRP or phonetogram. Graph that plots a person’s phonational range against his or her dynamic range
- football-shaped
- dynamic range shrinks @ high & low frequencies
