Hearing Aids Glossary

I gathered some common terms related to hearing aids and tried to explain them in a day to day language. Two important points I would like to emphasize:

First, the explanations here are all in hearing aids’ context. Meaning, the explanation doesn’t necessarily cover the term’s definition for other fields.

Second, for some of the terms, the explanation can go on forever. I tried to keep it short and simple and still have sufficient information.

The best way to look for stuff in this page is to search it. Use CTRL+F if you’re using windows.

Don't hesitate to contact us if you need further info. The terms are ordered alphabetically, give or take.



The basic hearing test equipment. Allows making sounds of different frequencies and varying intensities, to determine your hearing threshold over a range of frequencies.

Analog (hearing aid)

Hearing aid from “older” generations. Unlike digital hearing aid, the signal amplification is done without manipulating, and therefore the device is less sophisticated in his ability to deal with environmental noise, for instance.


Describes your hearing. A curve obtained in hearing test that describes the various frequency hearing threshold on both ears.

Automatic gain control

A component that automatically limits the maximum volume so the amplification will not be too much and cause inconvenience. Available on most hearing aids.


The heart of the hearing aid. Sounds are received by the microphone, transferred to the amplifier, where it is amplified and processed. The sounds are then transmitted to the receiver (the speaker).

Attack and release times

Attack time is the time between absorption of a sound increase and setting the right amplification.

Release time is the time between absorption of a sound decrease and setting the right amplification.

Getting these parameters better, improves how comfortable the hearing is.

Age-related hearing loss

(presbyacusis is the  professional word.) The most common hearing loss. It’s a sensorineural hearing loss, and it occurs symmetrically on both ears. Typically, the Higher frequencies are damaged  before others. As for how it influences the hearing, the hearing threshold will be higher and this will cause a degradation in speech understanding and issues on handling loud noises.

Audio shoe

AKA Audio boot. A small electronic device, that you can connect to your hearing aid using the Direct Audio Input (DAI) port. Typically, it fits the bottom of a BTE device and can be used as a stand-alone FM receiver or additional microphone. It can also be used as a connector for different audio sources like TV, music player etc (using cable, of course).


BERA test

Brain stem Evoked Response Audiometry (BERA), AKA Auditory Brain stem Response (ABR).

An objective test that evaluates how well does the signals are conducted from the inner ear, through the hearing nerve to the brain. It doesn't require the patient collaboration so you can do the test to toddlers and babies. It is also useful on cases where you want to find out the functionality of the brain stem.

It’s a fairly simple test, You lay down calmly, they attach some electrode to your forehead and behind your ears, you put on headphone and wait for 20-30 minutes till they finish the test.

BTE (Behind the Ear)

A hearing aid where the device itself (“Case”) is carried behind the ear. A tiny tube conducts the sounds from the case to the ear mold that’s located inside the ear canal.


supplies energy to hearing aids. Hearing aid’s batteries are available in few common sizes to fit the different devices. Most hearing aid’s batteries are Zinc-Air batteries. There are hearing aids with rechargeable batteries.



A vital part in hearing aids that allow it to overcome one of the major hearing loss issues - limited hearing range. On the one hand, you don’t hear silent sounds, on the other hand, loud noises can cause inconvenience. As a result, instead of hearing sounds from 0dB to 120dB (normal hearing), you can hear only from 50dB to 120dB (example). In this narrow range, the hearing aid must compress all the sounds and voices in your surrounding. The compression changes according to the volume of the sound it hears, unlike simpler hearing aids where all the sounds are amplified in the same manner.

Conductive (hearing loss)

A hearing loss Characterized by a malfunction in the outer or middle ear. The cause can be as simple as ear wax plug and can be a result of lack of parts of the outer ear, missing or damaged hearing bone or some structural issue in the hearing canal. It can also be due to a damaged ear drum or fluid accumulation behind the ear drum.

Conductive hearing loss is typically reversible. If not, on many cases, there is medical treatment to improve the situation.

Combined hearing loss

A hearing loss that combines a conductive hearing loss with a sensorineural hearing loss.


Hearing aids cleaning is essential. It is a delicate digital device, and it is exposed to sweat, ear wax, etc. Therefore, clean the hearing aid regularly, according to the hearing aids’ expert instructions. In addition, it’s good practice to bring it to the lab every few months for deeper cleaning and examination.

CIC (Completely In the Canal)

A hearing aid that is located in the ear canal, not visible to the outside. It is pulled outside using a small transparent chord attached to it.


Most hearing aids divide the frequency range they support to bands or channels. For instance, a naive distribution can be: channel A from 250Hz to 500Hz, Channel B from 500HZ to 1000Hz and so on. It gets much more than that in new hearing aids of course, this is just to illustrate the concept. There might be overlapping in the channels. i.e a given frequency can be allocated to two adjacent channels.

Hearing aids can amplify each channel differently, so the more channels, the merrier. More channels enable better tracking of the hearing loss pattern over the different frequencies (for instance: if you got hearing loss only on certain frequency, the hearing aid can amplify only this frequency).

In addition, specific channels can be filtered to handle noise on certain frequencies.

One indication of how sophisticate is your hearing aid is the number of channels, although the latest devices are handling the channels in a whole new way, not just having more and more of it.


A spiral organ, part of the inner ear, full with fluid. The hearing bones in the middle ear vibrate it mechanically and move the fluid. Hair cells in the Cochlea translate it to electric signals that are transmitted to the hearing nerve.

Many sensorineural hearing loss cases are caused by hair cell malfunction.


Human speaking sounds that you make by stopping air flow (unlike E, A, I, O, Y, U which are vowels). Our ability to understand human speech is based on the ability to distinguish between the different consonants. Basically, it requires good hearing above 2000Hz, although in order to distinguish between S and Z, for instance, you need sufficient hearing even on higher frequencies.

Corti (Organ of)

Part of the cochlea. Transforms the mechanical energy from the middle ear to electrical signals going to the hearing nerve. Accomplished using the hair cells in it.


Decibel (dB)

Sound level measuring unit. It describes the power of the sound. 0dB (for the sake of this explanation) is defined by the weakest sound a man can hear. It was established by testing  thousands of patients, for each of them finding the weakest sound they could possibly hear.

Given this basic hearing threshold (0dB), every patient having a hearing test is compared to this predefined sound level. If your hearing is OK, you can hear sounds as quiet as 0dB and as loud as 120dB. Generally speaking, if on some frequencies you can not hear 0dB sounds but rather only 20dB sounds or louder, you have a hearing loss.

Digital (Hearing aid)

An advanced way to process sounds. The sounds are transformed to bits, and you can then manipulate it as much as you want. Digital hearing aids are much more advanced when it comes to handling noise filtering and bad signal to noise ratio.

Directional mechanism

A system where a hearing aid gives higher priority (in amplification) to some sounds and suppresses other sounds. In most cases, speech voices, coming from the front are amplified, while sounds from the side and back are suppressed.

Direct Audio Input (DAI)

A three pin plug, the female are the three holes you can find on many BTE devices. Typically, due to its form factor, you can’t have it on tiny devices like ITE, ICC and others.

DAI enables you to connect all sorts of audio sources directly to your hearing aid. Sources can be a phone, TV, PC or music player.
Since it connects directly to the hearing aid, it bypasses the microphone (and the T-coil). As a result, this method is much less sensitive to noises.

DAI is also used to connect Audio shoes (AKA Audio Boots).


Ear mold

The part that’s located in the ear on BTE devices. It conducts the sounds from the hearing aid to your hearing canal. Ear mold doesn't perform any amplification. It is typically made of silicon, and its shape can vary according to your ear shape and how sealed you need it.

Eustachian tube

Connects the nasal cavity and pharynx (part of the throat behind the mouth) to the middle ear, keeping the ear ventilated and regulates the air pressure in it. The tube is open when you swallow and during extreme pressure changes (riding uphill or downhill, take off and landing).  If the nasal cavity is jammed (mocus, enlarged adenoid, swollen tonsils), the tube is blocked and pressure regulating is not at its best. This can cause some hearing loss, first due to vacuum in the ear and then due to fluids accumulating behind the ear drum. It’s one of the most widespread reasons to hearing loss among infants, toddlers and kids.

Ear drum

A delicate membrane that forms the limit between the outer ear and the middle ear. Sounds enter the ear canal, vibrating the ear drum and it transmits the energy to the hearing bones in the middle ear (ossicles) that are connected to it. There are hearing loss types that are caused by ear drum perforation (having a hole in the eardrum). You can sometimes fix it by a surgery called tympanoplastic surgery where you fix the tiny hole in a way somewhat similar to fixing a puncture in a car wheel.



The squeaky sound you can hear when a microphone absorbs some of the amplified sound. In the hearing aids’ world, it happens when a tone, that was already amplified, slips from inside the ear and finds its way to the microphone (outside the ear). This causes the tone to be amplified again and again by the hearing aid and eventually causes an irritating whistle.

In modern devices, they usually solve it without losing the hearing aid’s abilities.

Filter (Audio)

A common part of signal processing. In hearing aids, it enables you to amplify certain frequencies and ‘filter’ the other frequencies so they won’t be amplified. For instance, if you have only hearing loss on high frequencies, the lower frequencies will be filtered and won’t be amplified so you’ll hear them in its natural form.

Filter/shield (mechanical)

A component located on the hearing aid where the sound is transmitted to the ear canal. It protects the device from ear wax and dirt. Occasionally, a jammed filter can be the cause of performance degradation. Hearing aid expert can easily replace it.



Hearing test

Performed in room sealed to noises. Using a headphones, the technician plays series of sounds and words on different frequencies and different volume levels in order to define the patient hearing level.

Herzt (Hz)

A unit to measure frequencies. Something that ticks 10 times a seconds is said to be ticking on a 10 Hertz frequency. On a practical level, the frequency of a tone is how low or how high do we feel it. For instance, bird’s tweet is high frequency and a roaring motor is low frequency. In a hearing test, they test frequencies from 250Hz to 8000Hz. A human hearing, though, covers a wider range, from 20Hz to 20000Hz.

Hearing loss

A decrease in the ear’s sensitivity to sounds. A person with hearing loss requires higher volume in order to hear well, comparing to a person with no hearing loss. Hearing loss is characterized mostly by two parameters:

1) Severity - how much you have to increase the volume so the person could hear.

2) Type - where is the malfunction along the hearing path. A conductive hearing loss (outer or middle ear), a Sensorineural hearing loss (inner ear and/or hearing nerve) or any combination between the conductive and the Sensorineural.

Another option to define a hearing loss is to describe the different losses for the various frequencies. E.g. “high tone loss” will refer to hearing loss on higher frequencies.

Hair cells

The “heart” of the hearing organ is the organ of corti in the cochlea. It got hair-like cells that transform mechanical vibrations to electrical pulses.  Many sensorineural hearing loss cases are caused by hair cell malfunction.


Inner ear

The inner part of the ear. It includes the Cochlea (the snail-like hearing organ) and the organs of balance. The inner ear is connected to the brain with nerve fibers.

ITE (In The Ear)

A hearing aid that “seats” inside the outer ear and fills the pinna.

ITC (In The Canal)

A hearing aid that is placed in the canal. Its outer part can be seen on the entry of the canal.


A solution for deep hearing loss, where a simple hearing aid can’t help. Based on two main parts: 1) An electrode, inserted in a surgery to the cochlea  and triggers the hearing nerve directly. 2) Outer processor that gathers the sounds from the surrounding, processes it and transmits it to the electrode. This procedure is irreversible.





The way a sound level is perceived. The same objective volume can be perceived differently by different persons. Many times, persons with hearing loss, especially age driven, perceive medium volume sounds as unbearably loud.


The ability to tell where the sounds are coming from. It is based on the differences between our two ears’ hearing as the time and volume the two ears hear is slightly different. This is why bilateral hearing is so important and you have to overcome hearing loss in both ears. Moreover, it’s a reason to have a hearing aid for one ear even if the other ear is perfectly OK.

Lip reading

A means many hearing impaired people uses (and some hearing people on difficult listening conditions). This capability can be improved and learnt and it could certainly be a complement to information coming from the hearing aid.


Middle ear

The space between the ear drum and the inner ear. It includes three small bones named hearing bones or ossicles. The bones conduct the voice wave from the ear drum to the fluids in the inner ear.


A component that receives the sounds and voices from the surrounding and turns it to electrical signals with the right frequency and amplitude. Directional microphones give higher priority to sounds from a predefined direction on the expense of sounds from other directions. It enables the hearing aid to improve the ratio between ‘wanted’ signals and noise.


A situation where louder voices cover quite voices and prevent us from hearing it. On some hearing loss types, loud voices from a certain frequency run over voices from other frequencies and hence you can’t hear the whole spectrum. It easily influences your speech understanding.

Another ‘Masking’ is performed on hearing test. On these cases, they deliberately mask one ear with some noise to prevent it to ‘help’ the other ear.

MCI (Most Comfortable Level)

The sound volume that feels the most comfortable for a certain person. It’s a subjective parameter and it is very individual. For a person with good hearing, a normal conversation loudness will be the Most Comfortable Level.


Noise canceling mechanism

Background noises that the hearing aid amplifies is one of the widest spread reasons for abounding the device. Firms are constantly improving their noise cancellation mechanisms in order to improve this issue and to cancel the noises rather than amplify it. The hard part is to enable the hearing aid how to distinguish between wanted sound and un-wanted sounds (noise)



A clinical situation where one of the hearing bones (stapes) grows abnormally. It is usually common on the third decade of life, and it is more common with women. The disease got three stages, and eventually it could end up with a 40-50dB hearing loss. Treatment can be drugs, operation and/or hearing rehabilitation using hearing aids.

Outer ear

Contains the pinna and the hearing canal, all the way to the joint limit with the middle ear - the eardrum. The shape of the pinna got high importance in gathering the sounds from the surrounding and in focusing on its location.  The inch long hearing canal is bent to prevent foreign bodies to enter the ear. Ear wax is produced in the ear canal in order to protect it.

Open fit

A hearing aid with ventilation tunnel that goes through it. It allows low tones to pass through it. On the other hand, it amplifies the middle and high frequencies. Great for a high-tone-loss hearing impairment since it enables a more natural hearing without occlusion.

Output (sound level)

The signal strength emitted from the hearing aid’s speaker. It is a result of the input signal and the gain added by the hearing aid.



On some hearing aids, there is an option to define acoustics programs. Every program is characterized to fit a specific environment. For instance, you can have program for noisy places, program for a concert, a program for driving a car end so on. Usually, you can switch between the different programs with some button or a remote control. There are hearing aids that eventually learn your preferences and switch automatically from one program to another.




A phenomena that sometimes appear together with hearing loss. In this phenomena, a person with hearing loss feels that voices are louder than how they are perceived by a hearing person. Meaning, voices that a hearing person would define as “loud”, a person with hearing loss would define as “too loud”.

The consequences of this, is that the hearing range of a person with hearing loss is smaller comparing to a fully hearing person. Why? On the one hand, you can’t hear quiet voices (Assuming you got some level of hearing loss) and on the other hand, you can’t stand loud voices.

Real Ear Measurement (REM)

Measuring the sounds’ characteristics inside the ear. Keep in mind that hearing aids are developed on a generic ear that supposed to cover all ear types. The REM verifies that the hearing aid functions as expected once it is in your own specific ear.


Sound waves

Oscillation generated by a sound source, reaches the ear as a mechanical energy, carried by air, which triggers the eardrum as pressure.

Sensorineural (hearing loss)

A hearing loss Characterized by a damage to the inner ear or to the hearing nerve. This kind of hearing loss not only causing a higher hearing threshold but also harms the ability to distinguish between sounds. Among others, it affects the ability to understand human speech. Unfortunately, this type of hearing loss is usually not fixable. The cause can be age, noise, ototoxic medicine, hearing nerve tumor, congenital deafness and other diseases.

Signal to Noise Ratio (SNR)

The ratio between what we want to hear and the background unwanted noises. Generally speaking, the better the SNR, the better the speech understanding gets. All hearing aids try to improve SNR. Among other ways, a very common one is directional microphones that get sounds from few directions.

Shape (of hearing loss)

When performing a hearing test, you get an Audiogram, which describes the kind and severity of the hearing loss. In addition, there is a reference to the actual shape of the impairment as it appears on the Audiogram:

Flat - same threshold on all hearing frequencies.

HTL (High Tone Loss) - the hearing is OK till 2000Hz and descending on the higher tones. It can also start at 3000Hz and then it mentions “HTL, starting 3000Hz”.  The decent can be with a slight slope (named slopping, typical for hearing loss due to age) or with a steep slope (named SKI, typical to hearing loss due to noise damage).

LTL (Low Tone Loss) - Hearing loss on the lower frequencies. The medium and high frequencies are kept intact. It is common to state specific frequency where the decent starts, for instance: “LTL till 1000Hz (included)”. Typical to fluid accumulation behind the ear drum.

U shape - usually means either a proper hearing or a slight hearing loss that starts on the low tones, reaches a climate on the middle tones and gets back to normal on the high tones.

Corner - Hearing remains on the low tones, with no response on the middle and high frequencies.

Dead ear - No response on all frequencies. Practically, deafness.


Part of the hearing aid. Transforms the amplified electrical signal into acoustic energy. It sends the sounds to the ear canal. On many hearing aids, it is protected by some shield.

Sign Language

Many hearing impaired people, especially those with impairment from their first years, use sign language. Sign language differs from language to language (English sign language differs from the French, for example). Sign language is not a direct translation of the spoken language and has its own grammatical laws.

You can read more on American sign language here.



A symptom of an annoying sound (internal, not from external source) which on many cases comes with hearing loss. It is usually more bothering when it is quiet, when nothing can screen it. It is often related to a damage caused by exposure to noise. A common explanation is that as long as you hear OK, the voices from the surrounding screen this “internal noise” and once you lose your hearing, noting covers it. This is why on many cases, a hearing aid can help. It takes you out of the silence and brings sounds that can screen this irritating sound.


A short simple test to tell about the status of the middle ear. Air is gently blown into the ear with various air pressures. The ear drum’s response to the different conditions is measured. The way the ear drum reacts can tell on several problems in the middle ear.

Threshold (hearing)

The quietest sound a human can detect is defined as the hearing threshold. Hearing threshold is measured in dB and it is typically tested on few frequencies, ranging from 250Hz to 8000Hz (covering most of the human speech)


The tiny, transparent tube that conducts the sounds from the case of a BTE hearing aid to the ear mold. It should be flexible and clear, consider replacing it if it gets yellowish and rigid.


UCL (Un-Comfortable Level)

The maximum sound level that a patient can feel comfortable with. Just a bit louder beyond this level, the sound is un-comfortable.


Volume control

On many hearing aids, you can change the volume with a simple wheel or buttons.





Got a question?
Don't hesitate, ask!

We got a Q&A page, check it out here.