This glossary has been developed to help you understand key terms in audiology and music listening. Please let us know if you have any suggestions for improvement.
You can use the search box on the right to look up specific terms. You can also chose how many entries to display at a time using the dropdown box on the left.
A glossary of terms for music listening with hearing aids (Version 1.0, dated 4 Sep 2018).
| Term | Description |
|---|---|
| Amplitude | Amplitude/Intensity/Sound level/Level - These all refer to the physical measurement of the magnitude of sounds. Amplitude is related to pressure variations in the air. Intensity is related to the amount of power in a sound and is proportional to the square of amplitude or pressure. Sound level is a logarithmic measure of sound amplitude or sound pressure, and the usual unit is the decibel, which is abbreviated dB. Each time the amplitude is increased by a factor of 3.16 or the intensity is increased by a factor of 10, the sound level goes up by 10 dB. The decibel requires a reference level or “0 dB” point. The standard reference corresponds to a very low sound pressure of 20 m Pa, which is equivalent to 0.0002 dynes/cm 2 . With this reference, the sound level is referred to as the Sound Pressure Level (dB SPL). 0 dB SPL corresponds to a very weak sound, close to the weakest sound that can be detected for people with normal hearing. Average speech at a distance of one meter from the talker has a level of about 65 dB SPL and live music can reach levels in excess of 100 dB SPL. Meters (and even apps) are available to measure the sound level in dB SPL. |
| Amplitude compression (WDRC)/compression | The range of sound levels over which sounds are both audible and comfortably loud can be much smaller for people with sensorineural hearing loss than for people with normal hearing. Nearly all hearing aids deal with this by applying amplitude compression: the range of input sound levels to the hearing aid is squeezed into a smaller range of levels at the output of the hearing aid. When this compression processing works over a wide range of levels it is called “wide dynamic range compression” (WDRC). |
| Analogue hearing aid | Up to the early to middle 1990s, most hearing aids had analogue processing. The signal picked up by the microphone was amplified in a frequency-dependent manner using electronic components such as resistors, capacitors and inductors. The processed signal was sent to a miniature loudspeaker, often called a “receiver”. Despite the simplicity of the technology, analogue hearing aids could be effective. |
| Analogue-to-digital (A/D) converter | This is only found in digital hearing aids. An analogue-to-digital converter converts the analogue signal picked up by the microphone(s) to an equivalent digital (or numerical) representation, and the digital signal processor (DSP) operates on this digital representation. A/D converters are limited in the range of sound levels that they can deal with, and some of them introduce distortion for high-level sounds, such as fortissimo passages in music. The design of A/D converters has improved in recent years. |
| Assistive Listening Device (ALD) | This phrase refers to a wide range of devices that can work with a person’s own hearing aid or even without hearing aids. Some examples of ALDs are FM systems, infra-red systems, television listening systems, and loop systems. |
| Audiogram | This is a graphical measurement of the weakest sound that can be detected at different frequencies. The usual frequency range is from 250 Hz to 8000 Hz in one-octave steps (8 white notes on a piano or doubling of the frequency). Sometimes, hearing at higher frequencies (up to 16000 Hz) is assessed, as this may provide an early indication of noise-induced hearing loss. Normal hearing is plotted as a range around the references level of 0 dB HL. Increasing hearing loss is plotted downwards in an audiogram. |
| Bandwidth | Bandwidth refers to the frequency range over which a hearing aid can provide amplification (such as across the piano keyboard) from bass to treble. A narrow bandwidth may yield poor fidelity and sound quality. Most hearing aids provide amplification for frequencies from about 200 to 5000 Hz. It is difficult to provide amplification for frequencies below about 1000 Hz when an “open” fitting is used; this refers to a fitting with a large vent or opening, which allows sound to “leak” into and out of the ear canal. |
| Bone Anchored Hearing Aid (BAHA) | This is a hearing aid system where a pedestal or “abutment” is surgically implanted in the skull behind the ear. The BAHA clips onto the pedestal and applies vibration so that the sound is heard via the bones of the head. This is called “bone conduction”. BAHAs are used for people with primarily conductive hearing loss that has not been successfully treated by medical or surgical means. They are also used for people with severe unilateral sensorineural hearing loss (single-sided deafness). The BAHA is mounted on the deaf side. It picks up sounds from the deaf side and transmits them to the good ear via bone conduction. |
| Behind the ear (BTE) hearing aid | This type of hearing aid has its main components (microphones, signal processor and amplifier) in a small case behind the ear. The receiver may be in the BTE part, in which case the sound is fed to the ear canal via a tube. Alternatively, a plastic-encased wire may feed the signal to a receiver in the ear canal. The tube or receiver may be held in place by a custom-made earmold or by a soft dome whose size is chosen to fit the ear canal of the individual. |
| Bilateral | Bilateral/Unilateral. Most people derive significant benefit from two hearing aids. If a person is fitted with two hearing aids, then this is a “bilateral fitting”. If they only have one hearing aid, then this is a “unilateral fitting”. |
| Bimodal fitting | A bimodal fitting refers to having a cochlear implant in one ear and a conventional air conduction hearing aid in the other ear. The hearing aid is often used mainly to amplify low-frequency sounds. This can improve the sense of pitch and thereby improve the experience of listening to music. |
| Binaural | Binaural/Monaural - Binaural refers to listening with both ears. Monaural refers to listening with one ear only. Binaural hearing is important for the ability to judge the direction of sounds and for understanding speech when background sounds are present. |
| Bits | This refers to the number of possible amplitude values that are used in a digital hearing aid. Until recently, most digital hearing aids used a 16-bit system, which allowed representation of a range of sound levels of about 96 dB (for example from 10 dB SPL to 106 dB SPL), but recently 18- and 19-bit systems have been introduced. This increase in the number of bits allows the more intense parts of music to be processed without distortion. |
| Bluetooth | This is a specific wireless protocol that allows transmission of signals between hearing aids and other devices such as the television, telephone, or other assistive listening devices. Bluetooth typically has a 10 meter (35 foot) range and requires significant current from the hearing aid batteries. When Bluetooth in enabled, the battery life may be quite poor. |
| Cochlear Implant (CI) | A CI can restore some hearing to people with severe to profound or total hearing loss. Its operation depends on the survival of a proportion of the neurons that carry signals from the inner ear (the cochlea) to the brain. A CI requires implantation of a flexible wire containing a number of small electrodes. This electrode array is inserted into the cochlea via a small opening in the bony wall of the cochlea. An external part, which is held in place using a magnet under the skin, picks up the sound, processes it, and transmits electrical signals to a coil mounted under the skin. The transmitted signals are delivered to the electrodes in the form of brief electrical pulses. These stimulate the neurons and create a sensation of sound. Although CIs are often effective in improving the ability to understand speech, they convey only a poor sense of pitch, so their effectiveness for listening to music is limited. |
| Cochlear dead region | This describes a region in the cochlea where there are non-functioning inner hair cells and/or auditory neurones. These can be tested for using the TEN test (see Threshold Equalising Noise (TEN) Test ). |
| Completely In the Canal (CIC) hearing aid | Miniaturization of hearing aids over time has led to hearing aids that fit completely in the ear canal and where the most exterior portion is several millimetres inside the opening of the ear canal. Such aids are nearly invisible. |
| Conductive hearing loss | Hearing loss can come from many sources and from different parts of the ear. A conductive hearing loss comes from a problem of the outer ear (e.g. wax occlusion) or the middle ear (e.g. an ear infection). Conductive hearing losses can often be improved by surgery or medical intervention. |
| Damping | Depending on the material, shape and the size of an instrument or even the vocal tract (mouth and nose), energy is lost through friction and radiation of sound energy. This affects the way that notes decay for instruments like the piano or guitar, and it also limits the sharpness of resonances or formants. |
| Decibel (dB) | The decibel comes in several versions depending on the 0 dB reference point. For many measurements dealing with noise and music, the reference is 20 m Pa and the sound level is denoted dB SPL, as in 65 dB SPL. Sometimes the average detection threshold for young people with normal hearing is used as a reference. Sound levels with this reference are denoted dB HL or HTL (as in dB Hearing Level or dB Hearing Threshold Level). The audiogram, a standard hearing test, uses levels expressed in dB HL. |
| Decibel Level 50 dB SPL | This is a low sound level, typical of soft speech. |
| Decibel Level 65 dB SPL | This is a medium sound level, typical of conversational speech and music played “piano” (p). |
| Decibel Level 80 dB SPL | This is a high sound level, typical of speech in a noisy environment and music played “mezzo forte” (mf). |
| Decibel Level 95 dB SPL | This is a high sound level typical of shouted speech at close range and music played “forte” (f). |
| Digitally programmable hearing aid | Near the end of the era of analogue hearing aids, it became possible to have more than one “program” in a single hearing aid. The settings for the different programs were stored digitally, i.e. as numbers. The different programs could be selected usinga button on the hearing aid or via a remote control. These were replaced by digital hearing aids by the mid to late 1990s. |
| Digital Signal Processing (DSP) hearing aid | Digital hearing aids have a small computer that can use digital algorithms to process the sound. Because of this, digital hearing aids are more versatile and adjustable than older style analogue hearing aids. |
| Digital-to-analogue (D/A) converter | Digital hearing aids need to have a way of converting the processed digital signal back into a continuous or analog signal to create the amplified sound. A digital-to-analogue (D/A) converter does this job. In some hearing aids the D/A converter and receiver are combined. |
| Diplacusis (Dyplacusis) | Binaural diplacusis refers to the situation where a tone of a given frequency is heard with a different pitch in the left ear than in the right ear. It can occur to a small extent for people with normal hearing, but it is often larger in cases of sensorineural hearing loss. Sometimes, a single tone presented to one ear is heard as having two pitches. This is called monaural diplacusis. Both forms of diplacusis can adversely affect the enjoyment of music. |
| Directional microphone | Directional microphones in hearing aids help to pick up sound from specific directions. They are often used in speech-in-noise programs, for instance, to pick up more sound from the front direction where someone is speaking, and less from behind where there may be more background noise. In contrast, an omnidirectional microphone collects sound from every directional equally. Using a fixed omnidirectional microphone setting (or turning off the microphone adaptive directionality function) can therefore be problematic in noisy environments, but can help with music listening (e.g. for large musical ensembles which occupy more space, or for amplified sound presented through multiple, distant loudspeakers). |
| Distortion | This is a general term used to describe situations where the sound generated by a device (like a hearing aid) differs from the “ideal” sound. Technically, distortion usually refers to cases where there are frequency components present at the output of a device that were not present at the input. For example, if the input is a single frequency component at 1000 Hz, but the output has components at 2000, 3000 and 4000 Hz, this is called harmonic distortion. Some types of distortion are considered desirable; for example, some people like the “warm” sound of a valve amplifier, because of the type of distortion that it produces. In general, however, distortion in hearing aids is regarded as undesirable and manufacturers try to minimise it. |
| Feedback | The amplified sound generated by a hearing aid may get back to the microphone and be re-amplified. This circular process may lead to squeals or whistles, thereby introducing distortion and limiting the amplification that can be provided (as well as causing irritation to those near the user of the hearing aid). |
| Feedback Management System | One of the important features of modern digital hearing aids is that they have systems for reducing the amount of feedback in hearing aids. However, these systems can have undesired side effects when listening to music. |
| Frequency | Sound is caused by fluctuations or oscillations in air pressure. The number of complete oscillations of sound pressure per second is called the frequency of the sound. It has units Hertz (abbreviated Hz). Sometimes KiloHertz or kHz is used to denote 1000 ´ the frequency. 1 kHz is the same as 1000 Hz. Young children can hear tones with frequencies as high as 20,000 Hz (20 kHz), but as we age, the highest audible frequency decreases. The lowest audible frequency is often stated to be 20 Hz, although tones with even lower frequencies can be heard if they are very intense. The lowest audible frequency does usually not change much with age. The highest note on the piano has a frequency of about 4000 Hz and middle C has a frequency just above 250 Hz. |
| Frequency 250 Hz… actually 262 Hz is middle C on the piano keyboard | Audiologists hate it when frequencies are not nice round numbers. Even though middle C has a tonic at 262 Hz, audiologists tend to measure hearing at the closest round numbers, and so use 250 Hz rather than 262 Hz. |
| Frequency 4000 Hz… actually 4096 Hz is the top C on the piano keyboard | And again, audiologists tend to use the round number of 4000 Hz. |
| Frequency compression/frequency shifting | This is a technology where the high-frequency components of a sound are shifted or transposed to a lower frequency region where the hearing loss is smaller and the ear is operating more effectively. This is similar to pressing a piano key that would normally produce, say C5, and getting C4 instead. |
| Frequency response | Frequency response is the amount of amplification as a function of frequency. Many people have greater hearing loss at high frequencies than at low frequencies, and hence require more amplification at high frequencies than at low frequencies. The frequency response should vary smoothly with frequency. In some hearing aids, the frequency response is irregular and this can degrade sound quality. |
| Fundamental frequency | The tones produced by musical instruments and by humans when the vocal folds are vibrating are complex sounds that contain many “components” with different frequencies. For example, a typical tone produced by a male voice might have components at 200, 400, 600, 800, 1000,…Hz. Each component is called a harmonic, and the lowest harmonic is called the fundamental frequency. Men have average fundamental frequencies in the range 120 to 150 Hz. Women have higher fundamental frequencies and for children they are still higher. In music, the fundamental component is also called the tonic. |
| Gain (dB) | This is the formal name for “amplification”. Mathematically, it is the difference between the input sound level and the output sound level and it is measured in dB or decibels. Since it is a “difference” measure, it has no units after the decibel such as SPL or HL. The gain provided by hearing aids can be up to 70 dB. If the hearing aid attenuates the sound rather than amplifying it, as can happen at some frequencies, the gain is negative. |
| Hardware | This refers to the actual physical components used in hearing aids. These may include microphones, integrated circuits, receivers, and batteries. |
| Harmonics | Harmonics are regularly spaced tones or “frequency components” that make up the complex tones that occur in music. For example, middle C is at 262 Hz and a music note with this nominal frequency (called the fundamental frequency) has harmonics both at 262 Hz and at double this frequency (2 x 262 Hz), triple this frequency (3 x 262 Hz), and so on. The relative levels of the harmonics have a strong influence on the subjective quality (the timbre) of the note being played. |
| Hearing aid types | A range of different hearing aids are fitted according to individual hearing loss profile/needs (see Behind the ear (BTE) hearing aid, In The Ear (ITE) hearing aid, In The Canal (ITC) hearing aid, Completely In the Canal (CIC) hearing aid, Receiver In The Ear (RITE)/Receiver In the Canal (RIC), Bone Anchored Hearing Aid (BAHA)). |
| Hearing loss level | Hearing loss may occur in different degrees (see Slight hearing loss, Mild hearing loss, Moderate Hearing Loss, Moderately-Severe Hearing Loss, Severe Hearing Loss, Profound Hearing Loss ). |
| Hidden hearing disorder (and neural hearing disorder) | Some people report difficulties hearing in noise in excess of what would be expected given their audiogram. Indeed, such difficulties can occur even for a person with a normal audiogram. This is called “hidden hearing disorder”, because it is not revealed by the standard hearing test, the audiogram. Hidden hearing disorder may be related to subtle nerve damage. |
| Hyperacusis | Some people complain that certain sounds are too loud and bothersome despite them being at a sound level that most other people would not find to be bothersome. This heightened sensitivity to sound is called hyperacusis. While hyperacusis and tinnitus appear to be quite different phenomena, they often co-occur and the approaches to treating them are quite similar. |
| Intensity | Amplitude/Intensity/Sound level/Level - These all refer to the physical measurement of the magnitude of sounds. Amplitude is related to pressure variations in the air. Intensity is related to the amount of power in a sound and is proportional to the square of amplitude or pressure. Sound level is a logarithmic measure of sound amplitude or sound pressure, and the usual unit is the decibel, which is abbreviated dB. Each time the amplitude is increased by a factor of 3.16 or the intensity is increased by a factor of 10, the sound level goes up by 10 dB. The decibel requires a reference level or “0 dB” point. The standard reference corresponds to a very low sound pressure of 20 m Pa, which is equivalent to 0.0002 dynes/cm 2 . With this reference, the sound level is referred to as the Sound Pressure Level (dB SPL). 0 dB SPL corresponds to a very weak sound, close to the weakest sound that can be detected for people with normal hearing. Average speech at a distance of one meter from the talker has a level of about 65 dB SPL and live music can reach levels in excess of 100 dB SPL. Meters (and even apps) are available to measure the sound level in dB SPL. |
| In The Canal (ITC) hearing aid | Miniaturization of hearing aids over time has led to hearing aids that fit into the ear canal, with the outer part at the entrance to the ear canal. |
| In The Ear (ITE) hearing aid | Beginning in the early 1980s, integrated circuits (or ICs) became small enough to have everything encased in a shell that fits in the outer ear of the hearing aid wearer. With an ITE aid, the outer part of the aid is clearly visible. |
| Level | Amplitude/Intensity/Sound level/Level - These all refer to the physical measurement of the magnitude of sounds. Amplitude is related to pressure variations in the air. Intensity is related to the amount of power in a sound and is proportional to the square of amplitude or pressure. Sound level is a logarithmic measure of sound amplitude or sound pressure, and the usual unit is the decibel, which is abbreviated dB. Each time the amplitude is increased by a factor of 3.16 or the intensity is increased by a factor of 10, the sound level goes up by 10 dB. The decibel requires a reference level or “0 dB” point. The standard reference corresponds to a very low sound pressure of 20 m Pa, which is equivalent to 0.0002 dynes/cm 2 . With this reference, the sound level is referred to as the Sound Pressure Level (dB SPL). 0 dB SPL corresponds to a very weak sound, close to the weakest sound that can be detected for people with normal hearing. Average speech at a distance of one meter from the talker has a level of about 65 dB SPL and live music can reach levels in excess of 100 dB SPL. Meters (and even apps) are available to measure the sound level in dB SPL. |
| Level Dependent Gain (dB) | In most modern hearing aids the gain decreases as the input level to the hearing aid increases. For soft speech and music, the gain may be high, whereas for intense speech and music, the gain may be low. |
| Loop | Loop/T-Loop-Telecoil-Loop This is a relatively inexpensive assistive listening device where a loop of wire is placed around the outer perimeter of a room. A microphone is placed close to the desired sound source (e.g. a person giving a sermon in a church) and the amplified microphone signal is fed to the loop. People who are situated inside the loop can pick up the sound inductively (wirelessly) through their hearing aid telecoil(s). |
| Loudness | Loudness, is a subjective attribute related to the perceived strength of a sound. Loudness increases with increasing sound level, but it is also affected by frequency and the relative sound levels of the different frequencies in complex sounds like speech and music. |
| Monaural | Binaural/Monaural - Binaural refers to listening with both ears. Monaural refers to listening with one ear only. Binaural hearing is important for the ability to judge the direction of sounds and for understanding speech when background sounds are present. |
| Microphone/MEMS | Modern hearing aids (and mobile telephones) use miniature microphones that need to be stable regardless of age or changes in environmental conditions, such temperature and humidity. MEMS stands for Micro-Electro-Mechanical-System. MEMS microphones are increasingly being used in hearing aids. They can be fabricated using the same technology that is used to fabricate silicon “chips”, and they have high stability. |
| Mild hearing loss | This is hearing loss between 25 and 40 dB HL. In quiet one-to-one situations this usually does not create material difficulties, but noisy situations may pose a communication problem. |
| Mixed hearing loss | This refers to hearing loss that is a combination of conductive and sensorineural. |
| Moderate hearing loss | This is hearing loss between 40 and 60 dB HL. In quiet one-to-one situations there may be some communication problems and noisier situations pose a more severe communication problem. Most people with moderate hearing loss would benefit from wearing hearing aids. |
| Moderately-severe hearing loss | This is hearing loss between 60 and 75 dB HL. People with this degree of hearing loss will not understand speech at low to medium levels and require hearing aids for everyday communication. |
| MPO/SSPL90 | This refers to the Maximum Power Output that a hearing aid can generate. The MPO is usually reached when the input has a very high sound level, such as 90 dB SPL. Hence, the “Saturation Sound Pressure Level with 90 dB input” or SSPL90 is used to measure and set the MPO for each frequency. The MPO is usually set to avoid loudness discomfort for sounds with very high input levels. |
| Musical note names | Musicians denote notes by letters such as “A” and “C”. Audiologists and physicists denote notes by their fundamental frequencies. “A” corresponds to 440 Hz, and the “C” above that falls at 524 Hz. The two descriptions are equivalent but both are simplistic in that they ignore the higher frequency harmonics of the notes that determine their timbre. |
| Near Field Magnetic Induction (NFMI) | This is another form of wireless transmission where a magnetic field from an external device such as a telephone or streamer (worn by a hearing aid user) is picked up by the hearing aid using a special antenna. Unlike Bluetooth, this is very efficient and does not significantly compromise battery life. However NFMI, as the name implies, only functions if the external device is “near” the hearing aid. NFMI can also be used for communication between bilaterally fitted hearing aids, for example to synchronise programs or to allow the hearing aids to “focus” on sounds coming from a specific direction. |
| Occlusion | This refers to the sensation of increased loudness of sounds trapped within the ear canal and of self-generated sounds (e.g. speaking, chewing, swallowing) when the ear canal is blocked with an object such as hearing aids or protective ear plugs. Occlusion can make it difficult for musicians playing wind instruments to perceive a ‘natural’ sound with hearing aids. |
| Octaves | This is a frequency ratio of 2:1 and it is a basic interval in music and in speech. Two notes that are an octave apart (e.g. tones with fundamental frequencies of 262 and 524 Hz) sound similar and are given the same note name, for example “A”, sometimes with a number to define the exact frequency (e.g. A4 is an octave above A3). Tones that are an octave apart are separated by 12 semitones or 8 white piano notes. |
| Open-fitting | With open-fitting hearing aids, the earpiece does not fit tightly into the ear canal as it does with other types of traditional ear mould. Instead, it is a small, soft rubber (or silicone) dome which fits less tightly in the ear canal. This allows low frequency sound to escape and creates a more natural ear canal acoustic. Hearing aid users with open fitting may experience more feedback than those with a closed fitting, but they are less likely to experience occlusion. |
| Pitch | Pitch is a subjective attribute that allows us to judge a tone on a scale going from low pitch to high pitch. Variations in pitch convey a sense of melody. Higher frequencies tend to evoke higher pitches. Pitch can also be affected to a small extent by the intensity of the sound. |
| Profound hearing loss | This is hearing loss in excess of 90 dB HL. People with this degree of hearing loss would not be aware of speech at moderate levels and would require high-power hearing aids or cochlear implants. |
| Pure Tone Audiometry (PTA) | This test is a standardised test for identifying a person’s hearing threshold levels (the quietest sounds they can hear), and determining the degree, type and configuration of a hearing loss. PTA measures audibility of pure tone thresholds, but not other aspects of hearing such as sound localisation and speech recognition. |
| Receiver/loudspeaker | This is the component in a hearing aid that changes the electrical current back into sound. Many of the early designers of hearing aids came from the telephone industry and used the term “receiver” where most others would call this a loudspeaker or simply, a speaker. |
| Receiver In The Ear (RITE)/Receiver In the Canal (RIC) | These are BTE aids (see Behind the ear (BTE) hearing aid ) that have the receiver of the hearing aid situated in the ear canal, which has some acoustical advantages. A thin wire connects the BTE part to the receiver. |
| Real-ear Measurement (REM)/probe tube microphone measurements | This is a method of assessing sound pressure level in the ear canal using a calibrated probe tube (allowing an audiologist to measure what level of sound is present in the ear canal). REM is carried out to compare and verify the real-ear acoustical characteristics of a hearing aid with a prescription target. |
| Resonances/fat part | Based on the physical construction of a musical instrument there are certain frequency regions that are more intense than other regions. The frequency region with the greatest intensity is called the fat part. Physicists may call regions of increased intensity resonances or formants. For example, a flute may have a fat part around 880 Hz. It is very difficult to play this “A” note (just above the top of the treble clef) quietly. |
| Sampling rate (kHz) | The sampling rate is the number of times per second that the sound is sampled and converted to digital form by an A/D converter. The sampling rate limits the highest frequency that can be processed in a hearing aid, which is just below one half of the sampling rate. For example, if the sampling rate is 16,000 Hz, then the highest frequency that can be amplified is just below 8000 Hz. |
| Sensorineural hearing loss | Hearing loss arising in the inner ear and/or hearing nerve is called sensorineural hearing loss. Unlike conductive hearing loss, this type of hearing loss usually cannot be treated medically and it is usually permanent. Hearing loss due to aging, noise or music exposure is sensorineural. |
| Severe hearing loss | This is hearing loss between 75 and 90 dB HL. People with this degree of hearing loss may not even detect speech at normal conversational levels and require hearing aids to communicate at all. People with this degree of hearing loss may be candidates for cochlear implants. |
| Slight hearing loss | Hearing loss may occur in different degrees. Hearing is conventionally considered to be in the normal range if hearing thresholds are not greater than 20 dB HL. However, a slight hearing loss, between 15 and 25 dB HL, may affect the ability to hear in the classroom and may be educationally meaningful for young children. Adults with a slight hearing loss would not typically be aware of it. |
| Software | This refers to the computer programs or algorithms used in digital hearing aids or used to program and fit the hearing aids. |
| Sound level | Amplitude/Intensity/Sound level/Level - These all refer to the physical measurement of the magnitude of sounds. Amplitude is related to pressure variations in the air. Intensity is related to the amount of power in a sound and is proportional to the square of amplitude or pressure. Sound level is a logarithmic measure of sound amplitude or sound pressure, and the usual unit is the decibel, which is abbreviated dB. Each time the amplitude is increased by a factor of 3.16 or the intensity is increased by a factor of 10, the sound level goes up by 10 dB. The decibel requires a reference level or “0 dB” point. The standard reference corresponds to a very low sound pressure of 20 m Pa, which is equivalent to 0.0002 dynes/cm 2 . With this reference, the sound level is referred to as the Sound Pressure Level (dB SPL). 0 dB SPL corresponds to a very weak sound, close to the weakest sound that can be detected for people with normal hearing. Average speech at a distance of one meter from the talker has a level of about 65 dB SPL and live music can reach levels in excess of 100 dB SPL. Meters (and even apps) are available to measure the sound level in dB SPL. |
| Telecoil | Many, but not all, hearing aids have a built-in coil of wire that can receive external magnetic fields (by induction), such as from a telephone or a loop system. |
| Threshold Equalising Noise (TEN) Test | This test was developed to provide practitioners with a method of identifying cochlear dead regions. It involves measuring pure tone thresholds in a special masking noise, called the Threshold Equalising Noise. |
| Timbre | This term is used to describe the character or quality by which two sounds differ even when their pitch, loudness and duration are equal. This allows us to tell the difference, for example, between a violin and a piano playing the same note at the same volume. |
| Tinnitus | This refers to the perception of sound that is not caused by a physical sound source in the environment. Tinnitus can be ringing, buzzing, or noise-like. Tinnitus has many causes including hearing loss. While there is no cure, tinnitus can be managed with a combination of hearing aid amplification, sound generators, and psychotherapy. |
| Uncomfortable loudness level (ULL) | This is the highest level sound that a person can tolerate. It can be different for different frequencies. ULLs may be measured to help in programming hearing aids. They may also be used in diagnosing certain kinds of hearing problems such as “hyperacusis”. People with hyperacusis often have low ULLs. |
| Unilateral | Bilateral/Unilateral. Most people derive significant benefit from two hearing aids. If a person is fitted with two hearing aids, then this is a “bilateral fitting”. If they only have one hearing aid, then this is a “unilateral fitting”. |
| Vent | This refers to a hole in In-the-Ear hearing aids, or through the ear mould of BTE hearing aids. Vents allow escape of low frequencies, preventing the ‘blocked up’ feeling or ‘occlusion.’ |
Please cite this document as:
Chasin, M., Greasley, A. E., Crook, H., Beeston, A. V., and Moore, B. C. J. (2018). A glossary of terms for music listening with hearing aids. Version 1.0, dated 4 September 2018.
Links to archived versions of this document: