Praxis Random Ch3

Frequency

number of complete cycles occurring in a specified amount of time, measured in hertz (Hz)

What is the fundamental frequency?

the lowest frequency component of a periodic waveform or vibrating system, determining the perceived pitch of a sound

What is a formant?

natural resonance of the vocal tract

What is a harmonic?

A harmonic is a component frequency of a wave that is an integer multiple of the fundamental frequency, contributing to the wave's overall sound quality.

What is peak amplitude?

The peak amplitude is the maximum (positive or negative) extent of a wave's displacement from its rest position, indicating the strongest intensity of the sound wave.

what is the root mean square (RMS) amplitude?

Average signal strength across the entire signal; helpful for determining amplitude of complex signal (music, speech)

1) square amplitude values over length of the signal

2) calculate average of all amplitude values

3) find the square root of the average

What is phase?

the point in a cycle at which a vibrating object is located at a given instant in time

What is phase cancellation in hearing aid feedback?

When feedback is detected, signal of same frequency 180° out of phase is used to cancel feedback signal and reduce it

In reverberant sounds, what is lead and lag?

Lead - sound that arrives at the ear first

Lag - the echo or reflected sound subsequently arrives at ears

What is the precedence effect?

first-arriving (lead) sound dominates most of auditory perception

in binaural hearing: slightly delayed signal is not entirely ignored but may influence the precise localization of the sound source

echoes and reverberated sounds are minimized for a short period after the original sound

What is the ANSI reverberation standard for classroom?

Classrooms less than 10,000 ft have RT60 (time it takes from sound cessation for signal to decrease by 60 dB) values of ≤ 0.6 sec and ambient noise levels ≤ 35 dBA

What are two important features of digital signal processing (DSP)?

1) correctly capturing signal amplitude (amplitude quantization/resolution)

2) rate that this process occurs (sampling frequency)

TLDR: how accurately the analog signal is samples to reduce error and preserve integrity of the original signal to highest degree

Each bit provides how many dB in dynamic range for a digital system?

6dB

What is sampling frequency or sampling rate?

number of times per second amplitude quantization occurs

What is the Nyquist frequency?

effective sampling of a continous signal requires at least two samples per cycle

Sampling under the Nyquist frequency results in alias distortion

What is alias distortion?

introduction of lower frequency components to a signal that were not present in the original signal

2 ways to reduce effects of alias distortion

1) low pass filter the signal below the Nyquist frequency (anti-aliasing filter)

2) increase sampling frequency to increase the frequency at which aliasing distortion occurs

Describe DSP in HAs

Sound input is detected and processed by mic

Signal is converted into electrical signal

Electrical signal is amplified by preamplifier

Electrical/continuous signal is converted into digital (discrete) signal by analog-to-digital converter (ADC)

Processed by DSP chip (according to pt HL, device hx, UCLs)

Signal processed by digital-to-analog converter to convert back to analog

Analog signal simplified and transmitter to receiver (speaker)

present to pt

What are hits?

correct response when stimulus is present (sound is presented, individual responds)

What are misses?

Sound (of sufficient intensity suprathreshold) is presented, no response is provided

What are false alarms?

signal is absent, individual responds as if it is

What are correct rejections?

signal is absent, no response given

What is response bias?

internal judgement of how often and at what level is required for them to respond

What is a liberal response criterion?

listeners more likely to respond even if they are uncertain signal is present

Increase in hits, decrease in misses

Increase in false alarms, fewer correct rejections

What is a conservative response bias?

listener cautious to respond, often only responds suprathreshold

Increased missed, decreased hits

Increases correct rejections, fewer false alarmsWhat

What is d’?

discrimination index; quantifies the ease/difficulty of discrimination task

lower d’ = harder

What is ROC curve?

receiver operating characteristic curve plots false positives (x-axis) and true positives )y-axis); gives graphic presentation of performance on discrimination task with binary outcome

What is the method of limits?

changing one parameter of the stimulus by the person performing the assessment

Ex: audiologist changes intensity of the stimulus

What is the method of adjustments?

subject adjusts parameters of stimulus

Ex: Békésy audiometry

What is the method of constant stimuli?

two-alternative forced choice procedure; requires subject to make choice from two options

results given as percentage of time each level of signal was detected, gives psychometric function

What is validity?

the accuracy - how well a measure assess what it is intend to measure

What is reliability?

the consistency of a measure, the ability to measure similar results when the measure is repeated over time

What internal validity?

degree of confidence that the causal relationship being tested is trustworthy and not influenced by other factors or variables

What is external validity?

extent to which results from a steady can be applied to other situations, groups or events

What is ecological validity?

if test findings can be applied to real-world situations

What is construct validity?

test’s content, structure, variable associations, responses

What is content validity?

if a test measures what it is intended to measure

What is face validity?

if a test appears to measure what it is intended to measure

What is predictive validity?

a test’s ability to predict future behavior or performance

What is concurrent validity?

measures the ability to predict similar outcomes using different tests at the same time

What is test-retest reliability?

Consistency of results when repeating the same test on the same sample/individual at a different point in time

Ex: retesting 1000 Hz threshold at start and end of test

What is interrater (between rater) reliability?

extent to which different judges agree in their assessment

Ex: determining if the response is true during VRA

What is intrarater (within-rater) reliability?

consistency of observations/judgements of one rater over several trials

What is sensitivity?

how well a condition is detected when condition is present (relationship between true positives and false negatives)

What is specificity?

how well a condition is rejected when the condition is absent (relationship between false positives and true negatives)

What is frequency selectivity?

ability of the auditory system to process/resolve individual frequency components within a complex signal

ability depends on the width of the auditory filter (regions of aud system with narrower filters (LF) results in better freq selectivity compared to regions with wider filters (HF))

What is the effect of sound duration on audibility and spectral content?

threshold detection improves as duration of the stimulus is lengthened

Shorter signal = broader spectral content

longer signal = narrower spectral content

What is energetic masking?

any kind of acoustic energy obscuring a target; occurs in peripheral system

What is informational masking?

acoustic energy with meaningful content (speech, music, etc); occurs in peripheral and central aud system

What is the spatial release from masking?

changes in masker location relative to signal of interest (often speech) “release” or enhance the perception of the signal

What is modulation masking release or temporal glimpsing/dip listening?

when a masker fluctuates in amplitude over time and creates transient break in the noise from which information (tones, speech) can be extracted

slower modulation = longer glimpses

What does vertical localization rely on?

spectral cues as a function of head, torso and pinna as signal sources change in elevation

What does horizontal location rely on?

ITDs and ILDs

What are ILDs?

intensity level differences

dominate at high frequencies mostly due to head shadow effect

What are ITDs?

Interaural timing differences

difference in time between signal hitting closer ear vs further ear

What is MAF? What is MAP? Which is better?

minimum audible field (MAF): when auditory sensitivity is evaluated through a speaker

minimal auditory pressure (MAP) when auditory sensitivity is evaluated through headphones

MAF is better (lower thresholds) than MAP

What is a phon curve?

Graphically shows how perception of loudness varies across range of audible frequencies

Judges the perceived loudness of a given tone to be of equal loudness to a 1000 Hz tone on the same curve

What is recruitment

abnormal growth of perceived loudness

What processing do hearing aids due to help with recruitment/reduced dynamic range?

Wide dynamic range compression (WDRC), more gain for low-level sounds, less gain for moderate to loud sounds

what is the spectral theory of pitch perception?

pitch is derived from place of maximum basilar membrane excitation

what is temporal theory of pitch perception?

pitch is extraced from the temporal patterns of neural impulses evoked by the stimulus

Spectral theory of pitch perception dominates at which frequencies? Why?

high frequency; auditory neurons are unable to efficiently phase lock to signals above 1kHz and completely unable for frequencies above 5kHz

What is the residue pitch/case of the missing fundamental frequency? What does it support?

supports the temporal theory of pitch perception at the removal of the frequency components (F0 in this case) does not significantly alter the perception of pitch

relative distance between adjacent harmonics in frequencies above F0 creates a periodicity in the signal associated with F0 (from this pitch is preserved and extracted)

What test is done to test for presence of cochlear dead regions?

threshold-equalizing noise (TEN) test

wideband noise is spectrally shaped to given a constant masked threshold for a pure tone presented in the noise (remove neighboring regions contributing to threshold due to high intensity stimulation)

What are 6cc couplers used for? What does the coupler stimulate?

used with supra-aural headphones

stimulates average volume of adult ear canal with supra-aural headphones placed on ear

What are 2cc couplers used for? What does the coupler stimulate?

used to calibrate insert earphones and for electroacoustic analysis

What is the dBA weighting used for?

used to mimic human auditory sensitivity by frequencies at low intensities where low and high frequencies are attenuated

used for hearing conservation purposes

What is the RETSPL and RETFLs? When are they used?

reference equivalent threshold sound pressure levels

reference equivalent force levels

used to calibrate air (RETSPL) and bone (RETFL) conduction signals

represent signal levels required to reach absolute thresholds of hearing among otologically normal listeners (0dB HL or audiometric 0)

What is attenuator linearity?

predictable and equal change in audiometer output with changes in dB HL

What is harmonic distortion?

distortion occurring at integer multiples of a test frequency

What is crosstalk

where signal information from one channel is present and can be heard in other channel

What is rise-fall time?

time it takes for signal to go from off to on (rise time) and from on to off (fall time)

What is REUR?

real ear unaided response

ear canal unoccluded

REUG

real ear unaided gain

un-occluded ear, gives amount of natural gain provided by resonance properties of external auditory system

What is REAR

real ear aided response

HA in ear and turned on

What is REIG

real ear insertion gain

difference between aided and unaided ear canal (REAR - REUR); amount of gain provided by HA

what is RESR?

real ear saturation response

What is RECD

real ear to coupler difference

If a hearing aid has a sampling rate of 22kHz, at what frequency is distortion most likely to occur (according to the Nyquist theory)

11kHz