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Glossary

AGC

Automatic Gain Control (or Automatic Volume Control). A feature on a hearing aid that automatically adjusts the gain, depending either on the input level (AGC-I) or the output level (AGC-O). Also known as “Compression”.


AIDED RESPONSE

The reponse of a hearing aid in place on the ear. (Also called “In-situ Response”.) Subtract the “Unaided Reponse” from the “Aided Response” to get the Insertion Gain Response. When the Aided Response is measured in a real ear (as opposed to a manikin), it is called the “Real Ear Aided Reponse” (or “REAR”)


AMBIENT NOISE

The environmental sounds in a testing area.


AMPLITUDE

A measure of the magnitude of a signal.


ANECHOIC CHAMBER

A room with little sound reverberation; a room constructed to be acoustically absorptive


ANSI

American National Standards Institiute. A national organization that determines standards for testing equipment. A section number and date (year) following the initials “ANSI”, designate the standeard refferd to.


ARTIFACT

A false reading.


ASP

Automatic Signal Processing. A feature on a hearing aid intended to overcome the effects of background noise, making it easier to understand speech when noise is present. The term ASP is not standardized, and may refer to various forms of signal processing. Ususally, however, ASP refers to a reduction in low-frequency gain in the presence of ongoing background noise.


BATTERY SUBSTITUTION PILL

A battery simulator that conforms to the size and shape of a battery used in a hearing aid. It connects to the Battery Voltage Supply, providing the proper voltage to the hearing aid.


BERGER

A prescription formula developed by Kenneth W. Berger.


BIAS CHAMBER

The amplitude of the background frequency used in the Digital-Speech–in-Noise test


BIAS FREQUENCY

The background frequency, acting as noise, when using the Digital-Speech-in-Noise test


BI-CROS

A CROS aid that has two microphones, one at each ear, sending both signals to one ear


BLOOMING EFFECT

A characteristic of puretone testing at high levels, that typically shows low frequencies being amplified more than they are under normal use conditions.


BURST

The BURST signal (or Short Sweep on the FP35) presents short bursts of sound at ten frequencies: 250, 500, 750, 1000, 1500, 2000, 3000, 4000, 6000, and 8000 Hz. (On the FP35 200 and 700 Hz are used instead of 250 and 750 Hz.) This signal provides a quick way to determine the maximum output of the hearing aid with minimal discomfort to the patient. It can be used at lower amplitudes, as desired, but its big advantage is for testing maximum output. Since all the output of the aid is concentrated at one frequency at a time, testing with this signal gives you information on the worst-case performance of the hearing aid at each frequency, for any type of input signal. Noise reduction is automatically removed at 85 and 90 dB amplitudes since it is not necessary and makes the measurement take longer. Settling time is not used with BURST.


CALIBRATOR

A sound generator that produces a tone at a precisely controlled frequency and amplitude.


CIC COUPLER (Completely-in-the-Canal Coupler)

Completely In-the-Canal Coupler.A coupler designed to better handle the unique acoustic qualities of completely-in-the-canal aids. Included with the CIC Coupler is internal software which provides corrections to increase the accuracy of CIC measurements even further.


CONCHA RESONANCE

The major part of the acoustic effect of the pinna, contributing significant energy to the External Ear Effect in the region of 5000 Hz.


COIL

Abbreviation for telephone pickup coil.


COMPOSITE

A patented FONIX test tone consisting of 80 puretones presented simultaneously.


CONVERSION FORMULA

A hearing aid prescription formula, used to convert an audiogram to a target curve. Common formulas are the NAL, Berger, POGO, and the 1/2, 1/3, or 2/3 Gain rules.


CORFIG

Coupler Response for Flat Insertion Gain (or “correction figure”). This is the transformation that, when added to a target insertion-gain response will give the target coupler response. The inverse of “CORFIG” is “GIFROC”.


COUPLER

A device that connects a test microphone to a hearing aid to provide an accurate testing situation.


CROS

Contralateral Routing of Signal. A type of hearing aid that uses a wired or wireless system to send a signal to the opposite ear.


CURVE

A visual diagram of a measurement using two variables. In testing hearing aids, one variable may be frequency, shown on the horizontal axis of the curve, and the other variable amplitude, shown on the vertical axis of the curve.


DATA

Information.


DEFAULT

A choice automatically made by a computer program.


DIN CONNECTOR

A European-standard connector with pins surrounded by a round metal shell.


DISTORTION

Elements of a reproduced sound that deviate from the original.


EARCANAL RESONANCE

An acoustic property of the earcanal, often characterized by a peak at or near 3000 Hz. Along with the acoustic properties of the head, torso, and pinna, the Earcanal Resonance contributes significantly to the External Ear Effect.


EIN

Equivalent Input Noise. The amplitude of internal noise created by a hearing aid


ERROR

The latitude of inaccuracy in a testing system. It is usually expressed in +/- units and/or percent.


EXTERNAL EAR EFFECT

See Unaided Response.


FAST FOURIER ANALYSIS

A computer “short-cut” of the FOURIER TRANSFORM method for determining the frequency content of a signal.


FLAT WEIGHTED

Same as UNWEIGHTED, refering to a signal that has equal amplitude at every frequency.


FOURIER TRANSFORM

A mathematical procedure that changes “time” information into “frequency” information.


FREQUENCY

The number of vibrations or cycles per second of a periodic wave. The unit of measurement is Hertz (Hz).


FREQUENCY RESPONSE

A measure of the output of gain of a device across a range of frequencies of the input signal.


FUNDAMENTAL FREQUENCY

The lowest frequency in a harmonic complex tone, such as the FONIX Composite signal. The fundamental frequency determines the “pitch” of a tone.


GAIN

The amplification or increase in sound power in a hearing aid. In testing, it results from subtracting the level of the input from the level of the output of the aid.


GIFROC

The inverse of “CORFIG”. GIFROC is the transformation that, when added to a coupler response, will give the estimated insertion-gain response.


GRAPH

A grid of lines, with the vertical lines representing one set of information and the horizontal lines representing another. A “Curve” superimposed on a graph grid gives information about test results.


HAIC

Hearing Aid Industry Conference.


HARMONICS

Integral multiples of a puretone. The tone itself is the 1st harmonic, or fundamental frequency; twice the frequency of the tone is the 2nd harmonic; three times the frequency of the tone is the 3rd harmonic; etc.


HARMONIC DISTORTION

The presence of harmonics in a reproduced signal that are not present in the original signal.


HEAD BAFFLE EFFECT

Refers to the comparative augmentation of high-frequency sound caused by the acoustic diffraction of low-frequency sound by the head and pinna blending to produce a baffle.


HFA

High Frequency Average. According to ANSI S3.22, the averaged response at 1000, 1600, and 2500 Hz.


HL

Hearing Level. The amount of decibels above audiometeric zero at which a measured ear barely hears a sound.


Hz

Hertz. Unit of frequency, refering to cycles per second.


ICRA

International Collegium of Rehabilitative Audiology


IEC

International Electrotechnical Commission. An international organization that sets standards for measurements.


INSERT EARPHONE

Earphone whose transducer is joined to the ear by means of a tube attached to a foam eartip that is placed into the outer ear canal; used in finding Real Ear to Coupler Difference (RECD) measurements.


INSERTION GAIN RESPONSE

A measure of the acoustic benefit of a hearing aid, measured in a patient’s ear. The insertion gain is the difference, at any particular frequency, between the Aided Reponse and the Unaided Response. When considered across a range of frequencies, the measure is called the “Insertion-gain Response”. When measured in a real ear (as opposed to a manikin), the insertion-gain response is called the “Real Ear Insertion-gain Response” (or “REIR”).


IN-SITU

Latin for “in position”. In audiometery, it designates measurements taken with the hearing aid “in place” in the ear.


INTERMODULATION DISTORTION

Distortion generated by the faulty mixture of different input frequencies. This is a primary cause of harshness and lack of intelligibility in a hearing aid.


JIS

Japanese Industrial Standard; the organization which sets standards for measurements in Japan.


KEMAR

Knowles Electronics Mannequin for Acoustic Research; model, which nearly reproduces the acoustic qualities of an average adult head and torso, that is utilized in the assessment of hearing aid performance.


LED

Light Emitting Diode. A small pilot light on an instrument panel.


LEVELING

An automatic calibration procedure, establishing a “zero line” for measurements, taking into account all the acoustic properties of the test chamber or the testing room.


MENU

A list of choices offered by a computer.


MULTI-CROS

A hearing aid system that has a switch to select either a CROS, a BI-CROS, or a Monaural arrangement.


MZ COUPLERS

Modified Zwislocki Couplers. Three couplers based on the Zwislocki design, but sturdier; provided with In-Situ and OES options.


NAL

National Acoustic Laboratories of Australia.


NBS

National Bureau of Standards (U.S.), now known as National Institute of Standards and Technology.


NOISE REDUCTION

A way of producing a more stable reading by averaging many samples.


OCCLUDED RESPONSE

A frequency response measured inside the ear canal with the hearing aid earpiece in place, but with the hearing aid turned off. This is a measure of how much unamplified sound leaks into the ear through the earpiece (such as with an open fitting). When measured in a real ear (as opposed to a manakin), it is called the “Real Ear Occluded Response” (or “REOR”).


OCCLUSION EFFECT

Low-frequency intensification in the loudness level of bone-conducted signals resulting from the blocking of the ear canal.


OES

Occluded Ear Simulator. An option using three special couplers that provides the approximate data obtained with a standard ear simulator.


POGO

Prescription Of Gain and Output. A hearing aid prescription formula.


PROBE MICROPHONE

A miniature microphone with a thin, flexible tube that is inserted into an ear canal to measure sound.


REAL EAR MEASUREMENT

A measurement of sound pressure levels made with a probe microphone inside an ear canal.


REAL-TIME TESTING

The ability to view instantly the results of hearing aid tests.


REAR

Real Ear Aided Response. See “Aided Response”.


RECD

Real Ear to Coupler Difference. Measurement of the difference in decibels between the output of a hearing aid found with a probe microphone in the ear canal and the output of the aid found in a 2 cc coupler.


REFERENCE MICROPHONE

The microphone placed above the ear, which provides the reference measurement that is compared to that of the probe microphone placed in the ear canal.


REFERENCE POINT

The location in a test chamber where the microphone of a hearing aid must be placed for accurate testing.

REIR

Real Ear Insertion-gain Response. See “Insertion Gain”.


REOR

Real Ear Occluded Response. See “Occluded Response”.


RESONANCE

The tendency of an acoustic system to reinforce sounds of a certain frequency, the frequency determined by the shapes and sizes of the components of the system.


RESPONSE LIMIT

The high and low points of the frequency range found in the ANSI test sequence.


RESR

Real Ear Saturation Response. A special case of the REAR for which the hearing aid is operated at its saturation level. This is akin to the coupler measurement known as the “SSPL-90″.


REUR

Real Ear Unaided Response. See “Unaided Response”.


RMS

Root Mean Square. An overall measurement of the signal going in or coming out of a hearing aid. When measuring with Puretones, the RMS level at each individual frequency will be the same as the level shown at each frequency on a response curve. When measuring with a Composite Tone, the (overall) RMS level will be several dB higher than the level at each frequency on a response curve, since all the frequencies are presented at once.


SATURATION

The condition where any further increases in input level will yield no further increase in output level.


SMOOTHING

A “rounding-off” of a curve, removing minor peaks and valleys, to create a more readable curve, using a method that is equivalent to warbling the input signal.


SOFTWARE

The programming part of a computer system.


SPA

Special Purpose Average. According to ANSI S3.22, the averaged response at specially designated frequencies.


SPL

Sound Pressure Level. Expressed in decibels (dB), a logarithmic measure of the energy (amplitude) of a particular sound as compared to the energy of a specified reference sound.


SSPL (OSPL)

Saturation Sound Pressure Level. The greatest SPL that a given amplifier can produce.


SSPL-90 (OSPL-90)

Saturated Sound Pressure Level for an input of 90 dB SPL.


SWEEP

A sequence of puretone frequencies, which generates a frequency response curve.


TARGET

A curve based on an audiogram and a prescription strategy presenting the theoretically optimum response that a hearing aid should have for a particular hearing loss.


TELECOIL

A magnetic field used for testing the telephone pickup of a hearing aid.


UNAIDED RESPONSE

A frequency reponse measured inside the earcanal without a hearing aid in place. Also known as “External Ear Effect”, the Unaided Response consists of the combined acoustic affects of the head, torso, pinna, and earcanal. When measured in a real ear (as opposed to a manikin), it is called the “Real Ear Unaided Response” (or “REUR”).


UNWEIGHTED GAIN

A measurement of the amplification (gain) of an aid using an input signal (source) that has equal power across all test frequencies.


WARBLE TONE

A puretone with slight, but rapid, frequency variations.


WEIGHTED GAIN

A measure of the amplification (gain) of an aid, using an input signal (source) that has a spectral shape similar to that of the long term average of speech.


WEIGHTED POWER

The measurement of amplitude, in SPL, of the output of an aid, using an input signal (source) that has a spectral shape similar to that of the long term average of speech.


WHITE NOISE

A signal composed of all frequencies, which vary randomly in phase, each frequency having equal long-term energy levels.


WINCHAP

Computer Hearing Aid Program for Windows. A program designed to interface with FONIX instruments in order to make the storage of information in computer files quick and easy.

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