88 terms

chapter 4

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hearing assistive technology systems (HATS)
listening, alerting and or signaling devices that facilitate patients' communication with the environment or enhance their personal safety through the use of auditory, visual, or tactile modalities; encompass assistive listening devices and other assistive devices
signal processing
involves manipulation of various parameters of a signal
microphone
a transducer that converts an audio signal into an electronic signal
amplifier
increases the intensity of a sound
receiver
an instrument that converts electrical energy into acoustic energy, as in a hearing aid. the term also refers to the component of an FM system worn by the listener to receive signals from the FM transmitter
battery
a cell that provides electrical power
directional microphones
more sensitive to sound originating from in front of the user than to sound coming from behind the user
omnidirectional microphones
sensitive to sound coming from all directions
automatic directional microphones (ADMs)
automatically switch between an omnidirectional and directional mode according to environmental conditions
gain of a hearing aid
the difference in decibels between the input level of an acoustic signal and the output level
preamplifier stage
the signal from the microphone is amplified
signal processing stage
the signal is manipulated to enhance or extract component information
digital noise reduction (DNR)
processing designed to reduce gain in the low frequencies or specific frequency bands when noise is detected
output stage
the process signal is boosted
maximum power output (MPO)
the maximum intensity level that a hearing aid can produce, sometimes called saturation sound pressure level
peak-clipping
a method of limiting hearing aid output in which a constant or linear amount of gain is provided across a range of input levels until it reaches a saturation level, at which time the amplifier begins to "clip" off the peaks of the signal
saturation level
the point at which an amplifier no longer provides an increase in output compared to input
compression
a nonlinear form of amplifier gain used to determine and limit output gain as a function of input gain
on-off control
a small switch that moves back and forth to turn the hearing aid off when not in use and on when needed; may be incorporated into the volume wheel
direct audio input (DAI)
a hardwired connection that leads directly from the sound source to the hearing aid or other listening device
audio boot
aka a shoe, a device that is used with a behind-the-ear hearing aid for coupling to a direct audio input cord
telecoil
an induction coil that receives electromagnetic signals from a telephone or loop amplification system
MTO
an acronym that refers to the 3 settings of a hearing aid on- off switch; microphone, telephone, off
acoustic feedback
occurs when the output from a hearing aid receiver re-enters the microphone, sending the system into oscillation and creating a "squeal"
volume control
used to adjust its output
remote control
a handheld device that permits adjustments in the volume or changes in the program of a programmable hearing aid
multiple memories
allow the speech signal to be processed in more than one way
multiple memory hearing aids
allow the user to select the processing strategy according to the listening environment
acoustic feedback cancellation
a feature that avoids the annoying squeal produced by hearing aids when the microphone picks up the hearing amplified sound from the hearing aid and reamplifies it
multiple channels
filters the signal into frequency bands so that some bands (usually the high-frequency bands) can receive more gain than others
high-frequency directionality
entails the hearing aid microphone reproducing the effects of the pinna by amplifying high frequencies in a way similar to an ear that is not occluded with a hearing aid earmold, and thereby enhancing posterior/anterior and up/down localization
binaural gain control
aims to provide interaural difference cues, typically resulting from the head shadow effect, that are like those experienced in the unaided ears by means of wireless communication between the 2 hearing aids
body hearing aid
includes a box worn on the torso and a cord connecting it to an ear-level receiver
bone conductor
a vibrator or oscillator used to transmit sound to the bones of the skull by means of vibration
bone conduction hearing aid
delivers the amplified signal via a bone vibrator placed over the mastoid directly to the cochlea, bypassing the middle ear
behind-the-ear hearing aid
worn over the pinna and coupled to the ear by means of an earmold
earhook
connects the case of BTE the earmold tubing and hooks atop the ear
earmold
a coupler customized to fit into the auricle that channels sound from the earhook of a hearing aid into the auditory canal
contralateral routing of signals (CROS)
fitting is designed for unilateral hearing loss, and entails placing the microphone on the poor side and the amplifier and receiver on the good ear side so that sound can be routed to the good ear
bilateral contralateral routing of signals (BICROS)
fitting is designed for asymmetrical HL, and entails a microphone at each ear, with both microphones leading to a single amplifier and receiver in the better ear
in the ear (ITE)
hearing aid fits into the concha of the ear
in the canal (ITC)
hearing aid fits in the external ear canal, only partially filling the concha
occlusion effect
the enhancement of low-frequency sounds that occurs via bone conduction and is caused by the occlusion of the ear canal
bone conduction
delivers sound by means of vibrating the skull
completely in the canal (CIC)
hearing aid fits entirely within the external ear canal
ossicular chain
comprised of the 3 small bones of the middle ear, the malleous, incus and stapes, and extends from the tympanic membrane through the tympanic cavity to the round window
head shadow effect
attenuation of sound to one ear because of the presence of the head between the ear and the sound source
loudness summation
a summing of the signals received by each ear, resulting in a 3-dB advantage for binaural over monaural hearing
binaural squelch
an improvement in listening in noise when wearing 2 hearing aids instead of one, resulting in a 2-3 dB improvement in signal-to-noise ratio
localization
the ability to locate the source of a sound in space due to the normal ear's sensitivity to interaural differences in phase and intensity
bone-anchored hearing aid (BAHA)
a bone conduction hearing aid that is anchored in the mastoid and attached percutaneosly to an external processor and is often used for conductive hearing loss in the presence of chronic middle ear disorder or atresia
output sound pressure level (OSPL)
the maximum output generated by a hearing aid receiver, determined when the hearing aid has its gain turned full on and is receiving a 90dB SPL signal
loudness discomfort level (LDL)
the level at which sound is perceived to be uncomfortably loud
hearing aid test box
a chamber that provides an electroacoustic analysis of hearing aids and probe-microphone measurements. it provides an off-the-ear determination of OSPL-90 in which the hearing aid is connected to a 2-cc coupler to simulate the human ear canal; an input signal that sweeps across the frequencies at 90dB SPL is input, and the aid's output is measured.
gain/frequency response
the difference between the amplitude of the input signal and the amplitude of the output signal across frequencies.
prescription procedures
strategies for fitting hearing aids by using a formula to calculate the desired gain and frequency response
verification
to determine that the hearing aid meets a set of standards of basic electroacoustics, real-ear electrostatic performance and comfortable fit
probe microphone
a microphone transducer that is inserted in the external ear canal for the purpose of measuring sound near the tympanic membrane
real-ear measures
the use of a probe microphone to measure hearing aid gain and frequency response delivered by a hearing aid at the tympanic membrane
target gain
the gain prescribed for each frequency of a hearing aid, against which the actual hearing aid output is compared
speech mapping
a visual display of the impact of amplification on the average speech spectrum
validation
the extent to which hearing related disability has been reduced by an intervention, such as receipt of a hearing aid
hearing aid orientation
the process of instructing a patient (and a family member) to handle, use and maintain a new hearing aid
speech processor
the component of a cochlear implant where the input signal is modified for presentation to the electrodes in the electrode array
electrode array
a component of a cochlear implant composed of electrodes separated by insulation; it is inserted into the cochlea and placed in close approximation to the ganglion cells that are responsible for transmitting electrical impulses to those brain regions responsible for processing sound
round window
a membrane-covered opening between the middle ear space and the scala tympani section of the cochlea in the inner ear
multichannel
has more than one channel; present different channels of information to different parts of the cochlea
electrical auditory stimulation
presents combined electrical and acoustic stimulation to the same ear; developed for pateints who have profound hearing loss in the high frequencies and significant residual hearing loss in the low frequencies
hybrid
listening aids that combine a cochlear implant system with hearing aid technology
bimodal stimulation
the use of a cochlear implant in one ear and a hearing aid in the other
mapping
the process of programming the speech processor of a cochlear implant
electric threshold (T level)
the amount of current that must be passed through an electrode so that the patient is just aware of a sound sensation
maximum comfort level (c-level or M- level)
the maximum intensity level that can be listened to comfortably for a prolonged duration of time, sometimes referred to by the acronym MCL
loudness balancing
programming the speech processor so that stimulation follows the loudness contour or the incoming speech signal
pitch ranking
determines the ability to discriminate pitch from stimulation of the basal to apical electrodes
Frequency Modulation (FM
the process of creating a complex signal by means of sinusoidally varying a carrier wave frequency
personal FM system
a listening device in which the speaker wears a wireless microphone and the speech is frequency modulated in radio waves transmitted through the room to the listener who wears a receiver
FM boot
a boot-like device that houses an FM receiver. it attaches to the base of a behind the ear hearing aid
neckloop
a transducer worn around the neck, often as part of an FM assistive device system. it consists of a cord from a receiver and transmits signals via magnetic induction to the telecoil of the user's hearing aid
sound-field FM systen
a listening system in which sound from a microphone is transmitted to loudspeakers that are positioned throughout the room
infrared system
an assistive listening device that broadcasts from the sound source to a receiver/amplifier by means of infrared light waves
induction loop system
a system that works by running a wire around the circumference of a room or table that conducts electrical energy from an amplifier and thus creates a magnetic field, which induces the telecoil in a hearing aid to provide amplified sound to the user
closed caption (CC) decoder
in a tv or electronic appliance extracts previously encoded closed caption data from a received video signal an displays it on a screen
simple amplification systems
amplify the audio signal so that it is more audible to a person with a hearing loss
telephone amplifiers
amplify sound from a telephone receiver
hardwired assitive listening device
devices that are directly connected by wires
relay system
a system used by persons with significant hearing loss for telephone access; an individual contacts a relay operator who serves to transmit messages between the caller and the person called by means of teletype or voice
tactile aids
aids that transduce sound to vibration and deliver it ti the skin for the purpose of gross sound awareness and gross sound identification
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