Hearing Science test 2

complex periodic wave forms

sine, sawtooth, square and triangular -white noise is aperiodic b/c of random starting phases

spectral analysis

taking a complex periodic vibration and doing a fast foyer transform and telling what the frequency, amp and phases of all the individual components to make up that vibration -time domain---> the use FTT---> two frequencies present in

spectrogram

the display one gets from a spectrograph -plots frequencies along the Y axis and time along X axis -plots these frequencies as a function of time during some speech utterance that's inputted by speaking into a microphone -acoustically driven, input is derived as a combo of frequencies and amp and how they change with time

0 S/N

means both are the same level

Signal-to-noise ratio

-In our everyday world, we listen to sounds and speech (signal) in the presence of some interfering background sounds (noise). -ex)S= 75dB SPL; N=70 dB SPL? 75-70= +5 -ex) dB S=70 ; N = 75 dB SPL? 70-75= -5

intensity

-Intensity (I) = power/area (I = Pwr/A) -Power = rate of sound energy per unit time -Intensity, therefore, has units of W/m2

Decible

-defined as 10 times the log of the ratio of two numbers [ 10 log (xmeas/ref)]

early morning refraction

-In morning earth is cooler b/c the warmer air is higher and less dense which causes the sound waves to be refracted downward and then bounce off earth and then goes back downward -easier to hear early in the morning - reflected off the water and travel greater distances

equation for half-wave resonators

- fo = c/2L (string held on both ends); where c = speed of sound; L = length of string -Half-wave resonators generate resonant frequencies (F) at integer multiples of f0 -can get half a wave on length of a string

Tube Resonance= tube open at only one end

-(like the vocal tract!)= acts as a quarter wave resonator -A node has to occur at closed end where air can't move and an antinode has to occur at the open end where are can move freely.

normal conversational level of speech

-65dB SPL** -About 3o dB difference between loudest vowels and softest consonants in normal conversational speech

half-wave resonator

-A condition of resonance whereby the osseous spiral lamina through which the afferent nerve fibers leave the organ of court and enter the modules

pure tones

-AKA simple harmonic vibrations, sinusoidal vibrations, or sine waves -regular repetitive movements -can be described by their frequency, period, and starting phase

absorption

-Absorption is another opposition to the propagation of sound. -When sound is absorbed, the energy dissipates as heat and less is available to be reflected. The reflected wave is less than the original wave. -Any time a sound encounters an obstacle with a different impedance, there can be a trade off between how much is reflected and how much is absorbed.

Speech Acoustics

-Air flows from lungs, through vocal folds (with or without vibration) and into the oral and nasal cavities, which act as resonators. -Position and movement of the mouth, lips, tongue, jaw, and velum affects the resonance patterns of the vibrations in terms of frequencies, amplitudes, and timing. -Different speech sounds, therefore, have different acoustic properties that allows us to create speech that can then be encoded by the ear.

Damping

-Amplitude depends on the amount of force used to set the object into vibration, but the amplitude diminishes over time due to resistance. Resistance deteriorates the amplitude in an object over time. -amp declining ove time

Bandwith

-Bandwidth defines the range of frequencies at the 3 dB down points. BW = fu - fL -width of the filter or band between upper and lower cut off frequency -BW quantifies the narrowness or broadness of a filter

Absorption can be effected by _____?

-Different materials can result in different impedances and, hence, result is more or less absorption -frequency; some materials absorb high frequencies better than low frequencies -Thickness of material, greater thickness = greater absorption, but only between 250-2000 Hz.

wavelength

-Distance that a pure-tone travels in one cycle (distance between 2 points of condensation or 2 points of rarefaction). -Units are in meters, centimeters, or feet -Greek symbol lambda (λ) -λ=c/f -Dependent on speed of sound (c) in the medium

refraction: with the wind

-Faster wind speeds at higher heights cause wave to move faster than lower levels. Wave is refracted down to earth, then reflected up by the earth, and repeats this process.

refraction: against the wind

-Faster wind speeds at higher heights impede sound waves more than the slower speeds nearer the ground. Wave is refracted up and over the listener.

What is all of the sound sources have equal dB levels?

-If 4 sources each have a level of 72 dB IL, how many dB would the combined level be? dB IL (or SPL) = 72 + 10 log (4/1) dB IL (or SPL) = 72 + [10 log (2)+ 10 log (2)] dB IL (or SPL) = 72 + 3 + 3 dB IL (or SPL) = 78

dB Intensity Level (dB IL)

-If asked to calculate dB IL, the reference level is assumed to be 10-12 w/m2 -10 (-12th) is the standard reference level for intensity

dB Sound Pressure Level (dB SPL)

-If asked to calculate dB SPL, the reference level is assumed to be 20 µPa. -the standard reference level for pressure (20 µPa)

Wavelength in relation to diffraction

-If wavelength is small relative to object, more is reflected (less diffraction); -if wavelength is large relative to object, it essentially passes right around (more diffraction). -Diffraction varies inversely with frequency

beyond inverse square law

-Inverse square law only holds strictly in a free, unbounded medium with no obstacles. -If a sound wave encounters an obstacle, it can be: *reflected (bounces back) *diffracted (bends around an object) *refracted (bends as a result of medium changes) *absorbed (penetrated)

Resonance

-Natural (preferred) frequency of an object capable of vibrating; based on an object's mass and elasticity. Can be a solid object or air molecules as well. -Frequency of the object's vibration remains constant

pressure

-Pressure (p) = force/area (p = F/A) -Force = something that causes a change in the motion of an object. -units= N/m2 or Pascals (or µPa)

how do sound waves propagate from the source (what shape)

-Sound waves propagate spherically from the source, amp diminishes with distance b/c of friction and b/c at some distance the pressure won't be measurable b/c the energy is spread out over a large spherical circle -As sound travels further from the source, the sound pressure lessens because it is distributed over a larger spherical area. -Sound pressure will also diminish due to friction and objects in its path.

what's a sound

-Sounds are produced by something vibrating. -Examples: loudspeakers, guitar strings, vocal cords -Simple or complex and Regular or random -To propagate (travel), the medium that it is traveling through must also be capable of vibrating (can be air, fluids, or solids).

Upper and Lower Cutoff frequency

-The frequency above or below fc -where does the filter start cutting out -defined at 3dB down from center frequency peak (half power point)

Attenuation Rate (dB/octave)

-The rate at which energy changes for frequencies -whats the slope of the low and high frequency curve, how sharp is the curve -The slope of the filter curve, expressed in dB/octave. -Rejection rate or roll-off rate.

Resonator

-The receiving object is called a resonator. (the table you hit the tuning fork on) -The closer the frequency of the applied force to the natural frequency of the resonator, the greater the amplitude of the vibration (loudness increases).

Resonance: tuning fork example

-The tuning fork makes ringing sound at around 256 Hz, the certain density, mass and elasticity in the wood will respond to this forced vibration. -If there's a periodic sound on the table there is forced vibration. The sound decays rapidlya dn there is a trade off between amount of amp (resonance in this case), but it decays quicker. This is a way to amp sounds with natural vibrating characteristics of a particular sources or object. -The amplitude increases (sounds louder) for a short period of time EVEN THOUGH ENERGY HAS NOT BEEN ADDED.

Threshold of audibility

-Threshold sensitivity varies across frequencies -Most sensitive range 1000-3000 Hz. -human hearing range of frequency is 20-20,000Hz, diff sound pressures -diff amp along frequency range for us to barely hear sound which is called threshold

Diffraction

-Waves bend around the obstacle, reform, and continue beyond barrier. -or goes through an obstacle. Sound waves encounter a hole in the barrier and some energy is reflected back while others portions of the wave pass through, bend, and then reform beyond the barrier.

Starting Phase

-Where a vibration starts in a waveform it's cycle is called starting phase, e.g., 90, 180, 270 degree starting phases -can begin at any point in their range of movement and can go int he direction of either condensation or rarefaction -One complete cycle can be represented as angles around a circle ex) 180 degrees is starting at equilibrium and then goes to the rarefaction phase (negative phase) and then back to equilibrium -0 degrees starts when heading towards condensation phase, looks like a reversed 180 degree phase -if starting at 90 and other starts at 270 phase, they are 180 degrees apart and offset by a negative and wave cancels out

nodes

-a property of resonance where 2 interacting tones cause cancellation of sound

formant transitions

-aka formant frequencies -may be a raising or falling frequency transition depending on their proceeding or target consonant -combining semivowels and diphthongs are characterized by their formant transitions and most distinguished by their shifts in F2

time domain waveform

-amp as function of time -if have time domain waveform you can perform a spectral analysis and see individual components

How many dB IL is the upper limit of hearing?

-b/c the range of hearing in decibles is 140 dB, for either pressure or intensity is as calculated: -dB pressure= 20 log (10(7th)) or dB intensity=10log (10(14th)) -n dB IL = 10 log (10(14) -n dB SPL = 20 log (10(7)

90 and 270 starting phase

-beginning at 90 degrees means that the vibration begins from its point of max condensation and then beginning at 270 means that the vibration begins from its max point of rarefaction and then moves to equilibrium point and then to max condensation and then back to equilibrium and then back to max rarefaction -these two waveforms cancel each other out due to the exact opp. of of condensation and exact opp. of rarefaction which causes them to cancel out

vowels

-carry most of the audible energy in speech, and generally have lower frequencies, intensity of speech comes from vowels -complex voiced periodic vibrations -characterized by their F1 (height of tongue) and F2 (forward/back position of tongue) -Vowels are louder and lower in frequency than consonants; vowels carry the volume of speech

Filtering

-certain frequencies are excluded and certain frequencies are allowed to pass through -can be used to generate a sound that is composed of a specified range of frequencies by filtering out some portion of a wide range of frequencies

Root mean square

-common way to deal with amp in field of acoustics -Rms= .707* Ap -used to obtain an average amp. for the waveform

rarefaction

-decreased density of air molecules -decrease in sound pressure

cut off frequencies of filters

-define where the change occurs between those frequencies that are to be passed and those that are to be filtered out (octave slope) -defined a the point which is 3 dB less than the peak, called 3 dB down points or the half-power point

Inverse Square law

-describes the relation between the distance sound travels and the expected decrease in the level of the sound. -I = 1/d2 (d = change in distance), when doubleing distance intensity decreases b 1/4 and when quadrupling it decreases by 1/16 -p2 = 1/d2; p = 1/d (e.g., double distance), doubling distance pressure decreases by 1/2 and quadrupling in it decreases by 1/4

Spectrum definition

-division of a time domain waveform broken down into individual frequencies as a spectrum -plural of spectrum is spectra, adj. is a spectral analysis/representation -amp as function of frequency -spectral analysis of a waveform and shows frequencies at some amplitude -frequency domain

octave

-doubling of frequency -Refers to a doubling (2f) or halving (1/2f) of frequency -2000 Hz is one octave above 1000 Hz

Harmonic Series

-each sinusoid in the series must be an integer multiple (harmonic) of the lowest frequency component/fundamental frequency f(o). -the first harmonic is the same as the F0 ex) F0=125 Hz -1st harmonic =1x 125 Hz -2nd harmonic= 2 x f(0)= 250 Hz, also called 1st overtone) -3rd Harmonic= 3 x f(0)= 375 Hz, second overtone

absorption coefficient

-effectiveness of a material to absorb sound energy: Ratio of sound energy absorbed to the original sound energy can range from 0.0 to 1.0. -ex) coefficient of 0.4 means than 40% of the energy is absorbed.

equation for tube resonance open at only one end

-fo = c/4L -Harmonics are at odd integers of f0 ex) F1= 504 (1x F0) ex) F2= 1512 Hz (3x fo) ex) F3= 2520 Hz (5xfo)

cycle

-going through the points of a vibration's range of motion one time -vibration going through full range of motion -object from its starting point, to max peak, to negative peak, back to its starting point

band-pass filter

-has a band of frequencies that are passed -have high and low cut off frequencies defined by the Fc and defined by the dB octave slopes in the higher and lower frequency ranges

wavelength in relation to frequency

-higher frequencies as they travel are blocked by objects along the way -lower frequencies can more easily go around objects -why you can hear drums from far away rather than higher frequencies

Amplitude

-how far an object moves back and forth and the amount of max and minimum pressure created -the magnitude of a sound -the larger the magnitude the higher the amp -Amplitude (pressure) depends on force applied; greater force = larger amplitude -amp can be measured: peak amplitude (measure the amp from baseline to one of the peaks Ap), peak to peak (amp change that occurs between the positive and negative peak Ap-p) or Rms

Spectrograph

-how to analyze/plot the frequency, amp. and time characteristics of speech sounds all together -measures the spectra of speech sounds, words, or sentences in a relatively short window -amp is illustrated as the darkness within those frequency components

condensation

-increase in sound pressure -increased density of air molecules

logarithms

-logs are ratio scales where the reference must always be known and specified -logarithm of a ratio of two numbers is called the Bel -n dB = 10 log (Xmeas/Xref) ex) 1) n dB = 10 log (10-9/10-12) 2)10 log (103) 3) 10 (3) 4) n = 30 decibels (dB)

reference level for intensity and pressure

-lowest avg. intensity to hear a sound I= 1.0 x 10(-12th) p= 20 or 20 x 10 (0)

formants

-more intense frequencies with a darker band on the spectrogram, tonal areas -regions that vary depending on the resonance properties associated with the position of the articulators, the size of the vocal tract, dialect and duration of the vowels -concentrations of energy found in connected speech ad displayed on a spectrogram

aperiodic

-pattern of vibration doesn't regularly repeat itself over time, no periodical pattern, non-tonal noise -Wide range of frequencies ex)white noise -Can select/filter the frequencies to a narrower range of frequencies ex) filtered noise or narrowband noise -describe amp as a continuous line on a graph, as opposed to discrete frequencies which work with a period complex vibration

simple vibration

-periodic, regular, sinusoidal -known as pure tones -the vibratory pattern repeats at regular intervals

frequency

-rate of vibration, how fast is object moving back and forth, how fast does the eardrum move in and out after being struck -Hertz (Hz) = cycles per second (cps) and is the unit we will use for frequency. ex)1000 cps = 1000 Hz -The frequency of the rarefactions and condensations of air molecules is the same as the sound source.

two pure tones with the same frequency but with diff starting phases

-result in diff patterns of vibration resulting from the summation of the two original waveforms -produce places of cancellation when the points are in opposite phase directions or produces places of enhancement when the points are in the same phase direction -result in complicated wave forms

periodic waves

-simple or complex -periodic complex= add two sinusoids with diff frequencies but repeat themselves at regular intervals -complex tone but periodic so you can hear both frequencies

consonants

-sounds that contribute most to intelligibility as they proceed and or follow vowels to define words or parts of words -acoustic properties are more complicated then consonants -can be complex periodic or aperiodic and can be voiced or voiceless -Consonants generally are softer and higher in frequency than vowels, especially fricatives (s, f, th).

narrow band noise

-special type of band-pass filtered noise where there is a relatively restricted range of frequencies that sound like noise -these frequencies are often described by the width of the curve (filter is one third of an octave wide at 3 dB down points) as measured across the center frequency -used as noisemakers during hearing tests

band reject filter/notched filter

-specifies a range of frequencies in the middle of a wider range noise that are rejected -has a low and high rejection frequency point -those frequencies on both sides of the specified band rejected area are passed -used for a complex aperiodic or periodic vibration

refraction

-speed of sound changes based on density of medium -e.g., sounds going from air to water cause the speed of sound to increase (sound travels 4 times faster in water than in air). -This results in the waves being refracted (bent) and changes the direction of propagation.

what happens when a sound wave encounters an obstacle with a concave surface

-the reflected waves converge and sound energy is concentrated at a focal point. -concave surface: (

Relationship between duration and freqeuncy

-the shorter the stimulus duration the greater the frequency spreads (shows all frequencies) -duration effects spectral characteristics of a waveform -click= fast duration sound wave and only one frequency

what happens when a sound wave encounters an obstacle with a convex, dome, surface

-the spherical waves become more plane waves, and the reflected waves diverge and sound energy is scattered. -convex looks like this: )

Acoustics

-the study of the physical properties of sound in the environment, how they travel through air and how they're affected by objects in the environment

period

-the time (in seconds) that it takes to complete one cycle. -period and frequency are tied together -T in seconds = 1/f -F (in Hz) = 1/T (in seconds) ex) 20 Hz has a period of ? .05s or 50 ms

propogation

-the vibrating sound source sets up sound waves that travel through some elastic medium such as air and water and most solids -Propagation of sound occurs through back and forth vibrations of air molecules that begin nearest the source and spread to adjacent molecules. -b/c of the inertial and elastic properties of the air molecules, the air molecules only move in a localized region

What kind of waveforms cancel each other out

-two pure tones of the same frequency, but which are 180 degree out of phase with each other, (opposite phase directions) will cancel each other out

filters

-used to shape the spectra of noise stimuli and to focus on a specific frequency range that's to be analyzed -high pass, low pass, band pass and band reject

complex vibration

-when a sound is made up of more than one pure tone -the more pure tones you combine without the same starting phases, the more complex they become (not sinusoid) -simple sinusoids with different frequencies, amplitudes, and starting phases -tonal or buzzing quality

waveform

-when the pattern of movement is displayed with an amplitude as a function of time -time domain waveform= increase and decreases of air molecules in terms of an acoustic sound, easier to calculate period in a time domain wave form vs. a complex waveform -amp is on x axis and time is on y axis

overtone

-where you are above the fundamental frequency -first overtone is the second harmonic

Three steps to filtering

1) Amplitude spectrum of input signal. 2)System transfer function. 3) Amplitude spectrum of output signal.

logarithm rules

1) log ab = log a + log b 2. log a/b = log a - log b 3. log an = n log a 4. log 1/n = -log a

Parameters of a filter

1)Center (natural) frequency 2)Upper cutoff frequency 3)Lower cutoff frequency 4)Bandwidth 5)Attenuation (rejection) rate

speed of sound

343 m/s

Greatest amplitude occurs when the frequency of the applied force matches the ________?

Fnat (natural frequency) of the resonator

What would you expect wavelength to do as frequency gets higher?

shortens because cycles are closer together

postive S/N

signal is greater than the noise

square waves

Adding more and more sine waves with odd numbered harmonics -complex periodic wave

sawtooth wave

Adding more and more sine waves with successive harmonics (odd and even numbered) -complex periodic wave

spectrum

Amplitude as a function of frequency -amp is on x and frequency is on y

FTT

Any complex vibration can be analyzed through a Fourier analysis, i.e., fast Fourier transformation

Center (natural) frequency

Frequency corresponding to maximum amplitude of vibration. -peak of the filter

common audiometric frequencies

Hz: 250 s: .004 ms: 4 Hz: 500 s: .002 ms: 2 Hz: 1000 s: .001 ms: 1 Hz: 2000 s: .0005 ms: .5

Intensity and pressure related

I = p2 or p = √I

upper limit of pain for pressure and intensity

I= 100 w/m2 or 1 x 10(12th) p=200,000,000 or 20 x 10(7th)

Range (from least audible to upper limit @ 1000 Hz):

Intensity: 1.0 x 10(14th) w/m2 Pressure: 1.0 x 10(7th) µPa

Reverberant

Minimal absorption. "Echoey". Sounds bounce off walls and create non-ideal listening environments. In some cases, reverberation is planned/calculated to provide some desired effect.

negative S/N

Noise is greater than signal

Phase spectrum

Phase as a function of frequency -phase is on x and frequency is on y

tube resonance

Resonance and standing waves also occur in tubes due to interactions of the air molecule waves that are set into vibration. -Antinodes must occur at ends; -same equation as half-wave resonators b/c they are half-wave resonators -open on both ends

why does sound propagate

Sound propagates as a result of increases and decreases in the density of air molecules

more impedance to a sound means ______ sound absorption

The higher the impedance difference, the lower the sound absorption and the greater the reflected wave

Sound attenuating

Typical for hearing testing. Not complete absorption, but less expensive than anechoic.

quarter-wave resonator

a condition of resonance whereby the fundamental frequency is equal to a quarter wavelength (except for a tube open at one end)

speech banana

a representation of how different speech sounds are distributed on the audiogram

noise

an aperiodic vibration -lack of tonal quality

Anechoic

extremely high coefficients (fiberglass); nearly all sound is absorbed. Steel walls prevent any external sounds from entering (isolation). -very expensive

antinode

max amp combining resonant waves

The resulting amplitudes of the resonator will vary as a _______?

function of frequency.

If you add harmonics

if you add harmonics you get a periodic complex vibration -as you add more harmonics the waveform changes and the more you add you get a sawtooth waveform (combo of odd and even harmonics ), complex periodic vibration that takes shape that looks like sawtooth

high-pass filter

passes all the frequencies higher than the cut off frequency and rejects frequencies lower than the cut off frequency as defined by the dB octave slope toward the lower frequencies

low-pass filter

passes all the frequencies lower than the cut off frequency and attenuates frequencies higher than the cut off frequency as defined by the dB octave slope directed towards the higher frequencies

logs

ratio scales

less impedance to a sound mean _______ sound absorption

the lower the impedance difference, the higher the sound absorption and the lower the reflected wave.

mid day refraction

warmer air is lower and has more density. Sound waves are refracted upward and over heads of listener