Communication Acoustics

Question 1

A-Weighted Sound Level

Answer 1

Weighting most commonly based on octave filterbanks that account for human perception of loudness. It cuts off low and high frequencies, only very rough estimation. Used for Noise measurement or evaluation of risk of hearing loss. Technical very simple.

Question 2

Absolute Threshold

Answer 2

Minimum Sound Level of a pure tone that an average human with average hearing can hear with no other sound present. Reference point at 20 micropascals at 1kHz, 0dB SPL. Below an audiotory event does not exist

Question 3

Acoustic Horizon

Answer 3

Perceived distance of a sound, it approaches a limit of less than 10m asymptotically

Question 4

ADSR-Sequence

Answer 4

ADSR (Attack Decay Sustain Release), also called envelope for sound synthesis such as filter cutoff change over time. Characterizes sounds instruments ofver time. Found in analog synthesizers.

Question 5

Allophone

Answer 5

An allophone is a set of multiple possible spoken sounds, or phones used to pronounce a single phoneme.

Question 6

Approximant

Answer 6

In phonetics, a sound that is produced by bringing one articulator in the vocal tract close to another without causing audible friction. Also include semi-vowels suc as y in yes.

Question 7

Auditory Event

Answer 7

Internal events that often correspond to sound events. Auditory is subjectice.

Question 8

Auditory Nerve

Answer 8

One of the eight cranial nerves, consists of sensory fibres that conduct impulses from organs to hearing. Sends a spike (binary output, when receive enough neurotransmitter from hair cell)

Question 9

Auditory Stream

Answer 9

Streaming depends on the amount of difference between successive sounds and the rate of presentation of the sounds. Slow tempo - large intervals bound to single. Fast tempo, several streams are formed with same notes

Question 10

Bark Scale

Answer 10

Psychoacoustical Scale proposed by Eberhard Zwicker 1961. First Subjective Measurement of loudness. A frequency scale on which equal distances correspond with perceptually equal distances. Above 500Hz it is more logarithmic. Below 500 it becomes more and more linear. Bark = 25 + 75[1 + 1.4(fc/1000)^2]^0.69

100Hz for Low - then it increases with frequency

Question 11

Binaural Cues

Answer 11

Any difference of sounds arriving at two ears from a given soundsource. Acts as a cue to permit auditory localization. Most commonly ILD(IID) and ITD. Whereas the ITD is closely related to the IPD.

Question 12

Cepstrum

Answer 12

IFFT(Log of FFT) of speech, used to separate vocal tract information from pitch excitation in voiced speech. Describes the envelope of the spectrum

Inverse fouriert of logarithmic magnitude specteum

Question 13

Cochlear Amplifier

Answer 13

The cochlear amplifier refers to Outer Hair Cells and is the active amplification of mechanical motion.
The main component of the cochlear amplifier is the outer hair cell (OHC) which increases the amplitude and frequency selectivity of sound vibrations using electromechanical feedback

Question 14

Cochlear Implant

Answer 14

Electronical Device that stimulates the cochlear nerve.

Surgically implanted devices that transmits sounds to the cochlear nerve

Question 15

Concatenation Cost

Answer 15

Weighted sum of differences between predicted values and real values of the four boundary prosodic parameters. concatenation cost defines how well two
units combine when presented successively. This evaluation can be performed using a specially
weighted decision tree, where the cost is to be minimized.

Question 16

Critical Band

Answer 16

In audiology and psychoacoustics the concept of critical bands, introduced by Harvey Fletcher in 1933[1] and refined in 1940,[2] describes the frequency bandwidth of the “auditory filter” created by the cochlea. Roughly, the critical band is the band of audio frequencies within which a second tone will interfere with the perception of the first tone by auditory masking. Frequency region at which each inner hair cells best respond to, bandwidth depends on frequency

Question 17

Dichotic

Answer 17

Relating to or involving the stimulation of each ear simultaneously by different sounds

Question 18

Equal Loudness Curve

Answer 18

Is a measure of Sound Pressure Level over the frequency spectrum that a listener would perceive as constant loud when presented with a pure and steady tone. The unit is phon.

Question 19

ERB

Answer 19

The equivalent rectangular bandwidth or ERB is a Measure used in psychoacoustics, which gives an approximation to the bandwidths of the filters in human hearing, using the unrealistic but convenient simplification of modeling the filters as rectangular band-pass filters. {ERB}}(f)=6.23f^{2}+93.39f+28.52

Question 20

Fricative

Answer 20

A consonant sound that is made by forcing air through a narrow space: The /s/ in “said” and the /z/ in “zoo” are fricatives.
Turbulant airflow, voiced and unvoiced.

Question 21

Gammatone Model

Answer 21

A gammatone filter is a linear filter described by an impulse response that is the product of a gamma distribution and sinusoidal tone. It is a widely used model of auditory filters in the auditory system. Comes reverse correlation technique. Short coming: no level dependent characteristics, and slow on-set 30-18000

Question 22

Glottis

Answer 22

Thin opening between the vocal cords at the top of the larynx (= the organ in the throat), that is closed by the epiglottis when you swallow

Widest when breathing
Changed opening area during speech

Question 23

Hearing Level

Answer 23

SPL produced by and audiometer at specific frequency. Unit = Decibels.
Standardized reference that defines the lowest spl that causes an auditory event, frequency dependent.

If shifted more than 25dB, we speak of hearing impairment

Question 24

Hearing Treshold

Answer 24

Sound level below which a person’s ear is unable to detect any sound. It is usually 0dB. 20micro pascal Threshold shift is increase of hearing threshold in particular sound frequency. - Sensitvity decreases.

Question 25

Idiophone

Answer 25

Any musical instrument that creates sound primarily bt the vibration of the instrument itself. First of four main divisions. Bell, Xylophone

Question 26

Just Intonation

Answer 26

Tuning of musical intervals as whole number ratios (such as 3:2 or 4:3) of frequencies. Any interval tuned in this way is called a just interval. Just intervals (and chords created by combining them) consist of members of a single harmonic series of a (lower) implied fundamental.Purely based on triads.

Question 27

Linear Predictive Coding

Answer 27

Linear predictive coding (LPC) is a method used mostly in audio signal processing and speech processing for representing the spectral envelope of a digital signal of speech in compressed form, using the information of a linear predictive model.It is one of the most powerful speech analysis techniques, and one of the most useful methods for encoding good quality speech at a low bit rate and provides highly accurate estimates of speech parameters. LPC is the most widely used method in speech coding and speech synthesis.

Question 28

Loudness

Answer 28

The attribute of a sound that determines the magnitude of the auditory sensation produced and that primarily depends on the amplitude of the sound wave involved.Sounds are perceived with increasing strength of volume. Subjective feature is called loudness

Question 29

Median Plane

Answer 29

The median plane is a virtual plane between two loudspeakers. All points on the surface of that median plane are equidistant from both loudspeakers. … Being on the median plane means being equidistant from both loudspeakers. Median plane - vertical plane

Question 30

Method of Adjustment

Answer 30

In the method of adjustment, the subject is asked to control the level of the stimulus and to alter it until it is just barely detectable against the background noise, or is the same as the level of another stimulus. The adjustment is repeated many times. This is also called the method of average error.

Question 31

Modulation Transfer Function

Answer 31

The Modulation Transfer Function (MTF) describes to what extent the modulation m is transferred from source to receiver, as a function of the modulation frequency F, which ranges from 0.63 to 12.5 Hz. Hence, the MTF depends on the system properties and the background noise.

Objective measure of a communication channel required to compute the sti. It reflects how well the modulation of the envelope of narrowband signal is perserved when traveling from source to receiver

Question 32

Music Information Retrieval

Answer 32

MIR) is an interdisciplinary science aimed to studying the processes, systems and knowledge representations required for retrieving information from music. This music can be in symbolic format (e.g., a MIDI file), in audio format (e.g. an mp3 file), or in vector format (e.g., a scanned score). MIR research takes advantage of technologies and knowledge derived from
signal processing, machine learning, music cognition, database management, human-computer interaction, music archiving or sociology of music.

Question 33

Nasal Tract

Answer 33

Nasal is a feature which characterizes sounds that are produced by lowering the soft palate (=velum), allowing the air to escape through the nose. (Cf. damping for the spectral consequences of involving the nasal cavity in the articulation)

Question 34

Ossiclesi

Answer 34

The ossicles (also called auditory ossicles) are three bones in either middle ear that are among the smallest bones in the human body. They serve to transmit sounds from the air to the fluid-filled labyrinth (cochlea). The absence of the auditory ossicles would constitute a 
moderate-to-severe. Ossicle is lireally tiny bone. Though the term may refer to any small bone throughout the body, it typically refers to the malleus, incus, and stapes (hammer, anvil, and stirrup) of the middle ear.

Question 35

Otoacoustic emission

Answer 35

An otoacoustic emission (OAE) is a low-level sound emitted by the cochlea either spontaneously or evoked by an auditory stimulus. Specifically, OAEs provide information related to the function of the outer hair cells (OHC) (Stach, 2003). Over the past 20 years,
their use in routine audiological assessments has increased significantly.

Question 36

Outer Hair Cell

Answer 36

The human cochlea contains on the order of 3,500 inner hair cells and 12,000 outer hair cells at birth. The outer hair cells mechanically amplify low-level sound that enters the cochlea. The amplification may be powered by the movement of their hair bundles,
or by an electrically driven motility of their cell bodies. Effect is highest at low levels, actively amplifies vibration at the characteristic frequency.

Question 37

PEAQ

Answer 37

Perceptual Evaluation of Audio Quality (PEAQ) is a standardized algorithm for objectively measuring perceived audio quality, developed in 1994-1998 by a joint venture of experts within Task Group 6Q of the International Telecommunication Union’s Radiocommunication Sector, scale 1 to 5

Question 38

Phoneme

Answer 38

Unit of sound that distinguishes one word from another in a particular language. Phonemic tones are found in languages such as Mandarin Chinese, in which a given syllable can have five different tonal pronunciation.

Question 39

Pitch

Answer 39

Pitch is a perceptual property of sounds that allows their ordering on a frequency-related scale,[1] or more commonly, pitch is the quality that makes it possible to judge sounds as “higher” and “lower” in the sense associated with musical melodies.[2]
Pitch can be determined only in sounds that have a frequency that is clear and stable enough to distinguish from

Question 40

Pink Noise

Answer 40

Pink noise or ​1⁄f noise is a signal or process with a frequency spectrum such that the power spectral density (power per frequency interval) is inversely proportional to the frequency of the signal. In pink noise, each octave (halving or doubling in frequency) carries an equal amount of noise energy.

Question 41

Prosodyo

Answer 41

Prosody — the rhythm, stress, and intonation of speech — provides important information beyond a sentence’s literal word meaning. For example, prosody provides clues about attitude or affective state: The sentence “Yeah, that was a great movie,”
can mean that the speaker liked the movie or the exact opposite, depending on the speaker’s intonation. Intonation, Stress, Rhythm and timing (Variations of f0, pitch accent, division of words and phonemes in time)

Question 42

Roughness

Answer 42

Roughness is studied by examining how textures are perceived and encoded by an individual’s somatosensory system.[1] In an experiment to measure and compare the roughness of different sounds, listeners are presented with different sounds and asked to rate their roughness, for example on a rating scale. Recent research has displayed that there are two different codes, at least, for roughness: a vibrotactile code used for fine surfaces, and a spatial code used for coarse to medium surfaces. Fast modulation is perceived as roughness. Unit of roughness is asper. 1Khz, 60dB, 100% AM modulated at 70Hz is one asper. When frequency is larger than a critical band, roughness disappers. 15-300Hz, subjective psychoacoustic quantity

Question 43

Sound Event

Answer 43

Sound Stimuli that enter the auditory system

Question 44

Source–filter modell

Answer 44

The source-filter theory describes speech production as a two stage process involving the generation of a sound source, with its own spectral shape, which is then shaped or filtered by the resonant properties of the vocal tract.

Question 45

STIPA

Answer 45

The Speech Transmission Index for Public Address Systems, or STIPA, is a fast and accurate way to measure the STI of a given area, taking into account the quality of the speakers, signal interference, room acoustics.
Version of STI with simplified method and a test signal. Each octave band is modulated simultaneously with two modulation frequencies

Question 46

Spot Microphone

Answer 46

A microphone that is used to augment a stereo pair or other distant miking arrangement, to capture a single instrument or voice.

Question 47

Summing Localization

Answer 47

Summing localization occurs when two or more coherent sound waves arrive within a limited time interval and only one sound sensation is perceived. If the time variations are smaller than 1 ms, the time and level variations of all sound sources contribute to the direction of the perceived sound.

Question 48

Travelling Wav

Answer 48

Traveling waves are observed when a wave is not confined to a given space along the medium. The most commonly observed traveling wave is an ocean wave. vibrarion of the liquid of the basilar membran which carries signal content- a wave on the basilar membrane - a movement

Question 49

Vacil

Answer 49

Fluctuation strength is similar to roughness, though at much lower modulation frequencies. Fluctuation strength is measured in vacils, Fluctuation strength reaches its maximum at a modulation frequency of around 4 Hz. For much higher modulation frequencies, one perceives roughness rather than fluctuation. The reference value for one vacil is a 1 kHz tone, fully modulated at 4 Hz, at a sound pressure level of 60 decibels.

Question 50

Voiced sound

Answer 50

The waveform yielded by the speech production organs, the shape of the vocal tract and the glottis

Question 51

Diotic

Answer 51

When a signal is feed equally to both ears

Question 52

Diotic

Answer 52

When a signal is feed equally to both ears

Question 53

Timbre

Answer 53

Multi-Dimensional psychoacoustic measure

When you have same pitch, lohdness and durarion, timbre sets the tones apart