Devices similar to hearing aids include the osseointegrated auditory prosthesis (formerly called the bone-anchored hearing aid) and cochlear implant.
Real ear measurements (or probe microphone measurements) are an assessment of the characteristics of hearing aid amplification near the ear drum using a silicone probe tube microphone.
BTEs are generally capable of providing more output and may therefore be indicated for more severe degrees of hearing loss. However, BTEs are very versatile and can be used for nearly any kind of hearing loss. BTEs come in a variety of sizes, ranging from a small, "mini BTE," to larger, ultra-power devices. Size typically depends on the output level needed, the location of the receiver, and the presence or absence of a telecoil. BTEs are durable, easy to repair, and often have controls and battery doors that are easier to manipulate. BTEs are also easily connected to assistive listening devices, such as Frequency modulation systems and induction loops. BTEs are commonly worn by children who need a durable type of hearing aid.
Mini in canal (MIC) or completely in canal (CIC) aids are generally not visible unless the viewer looks directly into the wearer's ear.Eisenberg, Anne (24 September 2005) [https://www.nytimes.com/2006/09/24/business/yourmoney/24novel.html?ex=1164517200&en=dba8306ee44bce99&ei=5070 The Hearing Aid as Fashion Statement] . ''NY Times''.Dybala, Paul (6 March 2006) [http://www.audiologyonline.com/articles/article_detail.asp?article_id=1542 ELVAS Sightings – Hearing Aid or Headset] . AudiologyOnline.com. These aids are intended for mild to moderately severe losses. CICs are usually not recommended for people with good low-frequency hearing, as the occlusion effect is much more noticeable.Ross, Mark (January 2004) [http://www.hearingresearch.org/ross/hearing_loss/the_occlusion_effect.php The "Occlusion Effect" – What it is, and What to Do About it] , hearingresearch.org. Completely-in-the-canal hearing aids fit tightly deep in the ear. It barely visible. Being small, it will not have a directional microphone, and its small batteries will have a short life, and the batteries and controls may be difficult to manage. Its position in the ear prevents wind noise and makes it easier to use phones without feedback. In-the-canal hearing aids are placed deep in the ear canal. They are barely visible. Larger versions of these can have directional microphones. Being in the canal, they are less likely to cause a plugged feeling. These models are easier to manipulate than the smaller completely in-the-canal models but still have the drawbacks of being rather small.
In-the-ear hearing aids are typically more expensive than behind-the-ear counterparts of equal functionality, because they are custom fitted to the patient's ear.
In fitting, the audiologist takes a physical impression (Polyvinyl siloxane) of the ear.
The mold is scanned by a specialized Computer-aided design system, resulting in a 3D model of the outer ear.
During modeling, the venting tube is inserted.
The digitally modeled ''shell'' is printed using a rapid prototyping technique such as stereolithography.
Finally, the aid is assembled and shipped to the audiologist after a quality check.Sickel, K. et al. (2009) [http://www5.informatik.uni-erlangen.de/Forschung/Publikationen/2009/Sickel09-SMO.pdf "Semi-Automatic Manufacturing of Customized Hearing Aids Using a Feature Driven Rule-based Framework"]. ''Proceedings of the Vision, Modeling, and Visualization Workshop 2009'' (Braunschweig, Germany 16–18 November 2009), pp. 305–312
Individuals under the age of two (five in the USA) typically wear the BAHA device on a Softband. This can be worn from the age of one month as babies tend to tolerate this arrangement very well. When the child's skull bone is sufficiently thick, a titanium "post" can be surgically embedded into the skull with a small abutment exposed outside the skin. The BAHA sound processor sits on this abutment and Transmission (telecommunications) sound vibrations to the external abutment of the titanium implant. The implant vibrates the skull and inner ear, which stimulate the nerve fibers of the inner ear, allowing hearing.
The surgical procedure is simple both for the surgeon, involving very few risks for the experienced ear surgeon. For the patient, minimal discomfort and pain is reported. Patients may experience numbness of the area around the implant as small superficial nerves in the skin are sectioned during the procedure. This often disappears after some time. There is no risk of further hearing loss due to the surgery. One important feature of the Baha is that, if a patient for whatever reason does not want to continue with the arrangement, it takes the surgeon less than a minute to remove it. The Baha does not restrict the wearer from any activities such as outdoor life, sporting activities etc.
A BAHA can be connected to an FM system by attaching a miniaturized FM receiver to it.
Two main brands manufacture BAHAs today – the original inventors Cochlear Baha, and the hearing aid company Oticon.
This can also be achieved by using CROS hearing aid or bi-CROS style hearing aids, which are now wireless in sending sound to the better side.
;Spectacle hearing aids
These are generally worn by people with a hearing loss who either prefer a more cosmetic appeal of their hearing aids by being attached to their glasses or where sound cannot be passed in the normal way, via a hearing aids, perhaps due to a blockage in the ear canal. pathway or if the client suffers from continual infections in the ear.
Spectacle aids come in two forms, ''bone conduction spectacles'' and ''air conduction spectacles''.
;Bone conduction spectacles
Sounds are transmitted via a receiver attached from the arm of the spectacles which are fitted firmly behind the boney portion of the skull at the back of the ear, (mastoid process) by means of pressure, applied on the arm of the spectacles. The sound is passed from the receiver on the arm of the spectacles to the inner ear (cochlea), via the bony portion. The process of transmitting the sound through the bone requires a great amount of power. Bone conduction aids generally have a poorer high pitch response and are therefore best used for ''conductive hearing losses'' or where it is impractical to fit standard hearing aids.
;Air conduction spectacles
Unlike the bone conduction spectacles the sound is transmitted via hearing aids which are attached to the arm or arms of the spectacles. When removing your glasses for cleaning, the hearing aids are detached at the same time. Whilst there are genuine instances where spectacle aids are a preferred choice, they may not always be the most practical option.
;Directional spectacles
These 'hearing glasses' incorporate a directional microphone capability: four microphones on each side of the frame effectively work as two directional microphones, which are able to discern between sound coming from the front and sound coming from the sides or back of the user.[http://www.aarpinternational.org/agingadvances_sub/agingadvances_sub_show.htm?doc_id=553940 Netherlands: Dutch Unveil 'Varibel' – The Eyeglasses That Hear]
The first electrical hearing aid used the carbon microphone of the telephone and was introduced in 1896. The vacuum tube made electronic amplification possible, but early versions of amplified hearing aids were too heavy to carry around. Miniaturization of vacuum tubes lead to portable models, and after World War II, wearable models using miniature tubes. The transistor invented in 1948 was well suited to the hearing aid application due to low power and small size; hearing aids were an early adopter of transistors. The development of integrated circuits allowed further improvement of the capabilities of wearable aids, including implementation of digital signal processing techniques and programmability for the individual user's needs.
Note that telecoil coupling has nothing to do with the radio signal in a cellular or cordless phone: the audio signal picked up by the telecoil is the weak electromagnetic field that is generated by the voice coil in the phone's speaker as it pushes the speaker cone back and forth.
The electromagnetic (telecoil) mode is usually more effective than the acoustic method. This is mainly because the microphone is often automatically switched off when the hearing aid is operating in telecoil mode, so background noise is not amplified. Since there is an electronic connection to the phone, the sound is clearer and distortion is less likely. But in order for this to work, the phone has to be hearing-aid compatible. More technically, the phone's speaker has to have a voice coil that generates a relatively strong electromagnetic field. Speakers with strong voice coils are more expensive and require more energy than the tiny ones used in many modern telephones; phones with the small low-power speakers cannot couple electromagnetically with the telecoil in the hearing aid, so the hearing aid must then switch to acoustic mode. Also, many mobile phones emit high levels of electromagnetic noise that creates audible static in the hearing aid when the telecoil is used. A workaround that resolves this issue on many mobile phones is to plug a wired (not Bluetooth) headset into the mobile phone; with the headset placed near the hearing aid the phone can be held far enough away to attenuate the static. Another method is to use a "neckloop" (which is like a portable, around-the-neck induction loop), and plug the neckloop directly into the standard audio jack (headphones jack) of a smartphone (or laptop, or stereo, etc.). Then, with the hearing aids' telecoil turned on (usually a button to press), the sound will travel directly from the phone, through the neckloop and into the hearing aids' telecoils.
The American National Standards Institute (ANSI) has a ratings scale for compatibility between hearing aids and phones:
The best possible rating is M4/T4 meaning that the phone works well in both modes. Devices rated below M3 are unsatisfactory for people with hearing aids.
Computer programs that allow the creation of a hearing aid using a PC, tablet or smartphone are currently gaining in popularity. Modern mobile devices have all the necessary components to implement this: hardware (an ordinary microphone and headphones may be used) and a high-performance microprocessor that carries digital sound processing according to a given algorithm.
Application configuration is carried out by the user himself in accordance with the individual features of his hearing ability. The computational power of modern mobile devices is sufficient to produce the best sound quality. This, coupled with software application settings (for example, profile selection according to a sound environment) provides for high comfort and convenience of use.
In comparison with the digital hearing aid, mobile applications have the following advantages:
2.4 gigahertz Bluetooth connectivity is the most recent innovation in wireless interfacing for hearing instruments to audio sources such as TV streamers or Bluetooth enabled mobile phones. Current hearing aids generally do not stream directly via Bluetooth but rather do so through a secondary streaming device (usually worn around the neck or in a pocket), this bluetooth enabled secondary device then streams wirelessly to the hearing aid but can only do so over a short distance. This technology can be applied to ready-to-wear devices (BTE, Mini BTE, RIE, etc.) or to custom made devices that fit directly into the ear.
Many theatres and lecture halls are now equipped with Assistive Listening Devices that transmit the sound directly from the stage; audience members can borrow suitable receivers and hear the program without background noise. In some theatres and churches FM transmitters are available that work with the personal FM receivers of hearing instruments.
Many hearing aids now have both an omnidirectional and a directional microphone mode. This is because the wearer may not need or desire the noise-reducing properties of the directional microphone in a given situation. Typically, the omnidirectional microphone mode is used in quiet listening situations (e.g. living room) whereas the directional microphone is used in noisy listening situations (e.g. restaurant). The microphone mode is typically selected manually by the wearer. Some hearing aids automatically switch the microphone mode.
Adaptive directional microphones automatically vary the direction of maximum amplification or rejection (to reduce an interfering directional sound source). The direction of amplification or rejection is varied by the hearing aid processor. The processor attempts to provide maximum amplification in the direction of the desired speech signal source or rejection in the direction of the interfering signal source. Unless the user manually temporarily switches to a "restaurant program, forward only mode" adaptive directional microphones frequently amplify the speech of other talkers in a cocktail party type environments, such as restaurants or coffee shops. The presence of multiple speech signals makes it difficult for the processor to correctly select the desired speech signal. Another disadvantage is that some noises often contain characteristics similar to speech, making it difficult for the hearing aid processor to distinguish the speech from the noise. Despite the disadvantages, adaptive directional microphones can provide improved speech recognition in noise
FM systems have been found to provide a better signal to noise ratio even at larger speaker-to-talker distances in simulated testing conditions.
A T-coil consists of a metal core (or rod) around which ultra-fine wire is coiled. T-coils are also called induction coils because when the coil is placed in a magnetic field, an alternating electric current is induced in the wire (Ross, 2002b; Ross, 2004). The T-coil detects magnetic energy and transduces (converts) it to electrical energy. In the United States, the Telecommunications Industry Association's TIA-1083 standard, specifies how analog handsets can interact with telecoil devices, to ensure the optimal performance.[http://ftp.tiaonline.org/UPED/20070717/UPED-20070717-010_TIA-1083_Flyer.pdf TIA-1083: A NEW STANDARD TO IMPROVE CORDLESS PHONE USE FOR HEARING AID WEARERS] . U.S. Telecommunications Industry Association
Although T-coils are effectively a wide-band receiver, interference is unusual in most hearing loop situations. Interference can manifest as a buzzing sound, which varies in volume depending on the distance the wearer is from the source. Sources are electromagnetic fields, such as CRT computer monitors, older fluorescent lighting, some dimmer switches, many household electrical appliances and airplanes.
The states of Florida and Arizona have passed legislation that requires hearing professionals to inform patients about the usefulness of telecoils.
"Essential" phones are defined as "coin-operated telephones, telephones provided for emergency use, and other telephones frequently needed for use by persons using such hearing aids." These might include workplace telephones, telephones in confined settings (like hospitals and nursing homes), and telephones in hotel and motel rooms. Secure telephones, as well as telephones used with public mobile and private radio services, are exempt from the HAC Act. "Secure" phones are defined as "telephones that are approved by the U.S. Government for the transmission of classified or sensitive voice communications."
In 2003, the FCC adopted rules to make digital telecommunications wireless telephones compatible with hearing aids and cochlear implants. Although analog wireless phones do not usually cause interference with hearing aids or cochlear implants, digital wireless phones often do because of electromagnetic energy emitted by the phone's Antenna (radio), backlight, or other components. The FCC has set a timetable for the development and sale of digital wireless telephones that are compatible with hearing aids. This effort promises to increase the number of digital wireless telephones that are hearing aid-compatible. Older generations of both cordless telephone and mobile phone phones used analog technology.
The signal processing is performed by the microprocessor in real time and taking into account the individual preferences of the user (for example, increasing bass for better speech perception in noisy environments, or selective amplification of high frequencies for people with reduced sensibility to this range). The microprocessor automatically analyzes the nature of the external background noise and adapts the signal processing to the specific conditions (as well as to its change, for example, when the user goes outside from the building).
For users with varying degrees of hearing loss it is difficult to perceive the entire frequency range of external sounds. DHA with multi-channel digital processing allows a user to "compose" the output sound by fitting a whole spectrum of the input signal into it. This gives users with limited hearing abilities the opportunity to perceive the whole range of ambient sounds, despite the personal difficulties of perception of certain frequencies. Moreover, even in this "narrow" range the DHA microprocessor is able to emphasize the desired sounds (e.g. speech), weakening the unwanted loud, high etc. sounds at the same time.
Advantages of digital aids include:
According to researches DHA have a number of significant advantages (compared to analog device hearing aids):
The invention of the carbon microphone, transmitters, digital signal processing chip or Digital signal processor, and the development of computer technology helped transform the hearing aid to its present form.Howard, Alexander (26 November 1998). [https://www.nytimes.com/1998/11/26/technology/hearing-aids-smaller-and-smarter.html "Hearing Aids: Smaller and Smarter."] The work was conducted with the help of the "big" computer of that time. Although they could not claim to be a real hearing aids (their performance was not enough for audio processing in real time – not to mention the size), they carried out successful studies of the various hardware circuits and algorithms for processing audio signals. The software package BLODI (stands for Block of Compiled Diagrams) developed by Kelly, Lockbaum and Vysotskiy in 1961 allowed to simulate any sound system provided in the form of a block diagram. With its help a special phone for users with hearing impairments was created. In 1967, Harry Levitt used BLODI to simulate a hearing aid on a digital computer.
Almost ten years later the second step was taken – the creation of "quasi-digital" hearing aid, in which the analog components and digital programmable module was combined into a single compact case. In this device the digital controller not only controlled the analog components (amplifiers, filters and signal limiter), but it could be programmed by connecting an external computer (in the laboratory – with medical supplies of hearing aids).
The concept of quasi-digital device was very successful from a practical point of view because of the low power consumption and compact size. At that time, low-power analog amplifier technology was developed very well – in contrast to the semiconductor chips necessary for a "real" digital camera. The combination of high performance analog components and digital signal processing capability has led to the creation module successful production parts.
The hearing aid of this type was developed by Etymonic Design. A little later, Mangold and Lane created a programmable multi-channel hearing aid. A similar approach was applied by Similarly, Graupe with co-authors for developing of an adaptive noise filter on a single crystal. This relatively small chip had low power consumption and fit in the case of ordinary BTE or ITC hearing aid.
The third stage of development was the appearance of "real" digital hearing aids. In DHA all stages of sound processing are carried out in binary form. To do this, an external sound from a microphone first converted into a binary code, and after the conversion the reverse transformation is carried out (to analog signal transmitted by the ear speaker in the form of sound). The first "real" DHA were models developed by Graup in 1970 on the basis of the 8080 microprocessor, which replaced the analog components (amplifier, limiter and filters). The possibilities of a programmable processor made the device self-adjusting, which opened the prospects for the use of advanced signal processing techniques, noise reduction, etc. Although the 8080th processor was relatively slow and big in size.
Further development of the DHA is associated with the creation of microprocessors with parallel processing of data arrays. As a result, a significant decrease of calculations time gave the opportunity to conduct processing of audio signal in real time. The small size of microchips (as of 1987) allowed creating compact hearing aids not exceeding the dimensions of their analog "predecessors" on their basis. However, for ITC aids these processors were not yet sufficiently compact. In all other respects, "full" DHA of that period was very similar to modern models.
Hearing aids are provided by the State to children, OAPs and to people whose income is at or below that of the State Pension. The Irish State hearing aid provision is extremely poor; people often have to wait for two years for an appointment.
It is estimated that the total cost to the State, of supplying one hearing aid, exceeds €2,000.
Irish taxpayers can also claim tax relief, at the standard rate, as hearing aids are recognised as a medical device.
Hearing aids in the Republic of Ireland are exempt from VAT.
Hearing aid providers in Ireland mostly belong to the Irish Society of Hearing Aid Audiologists.
Several industrialized countries supply free or heavily discounted hearing aids through their Publicly funded health care.
Within the UK, the National Health Service provides digital BTE hearing aids to NHS patients, on long-term loan, free of charge. Other than BAHAs (Bone anchored hearing aid), where specifically required, BTEs are usually the only style available. Private purchases may be necessary if a user desires a different style. Batteries are free.[http://www.rnid.org.uk/VirtualContent/101701/NHS_hearing_aid_service_September_2009.pdf NHS hearing aid service fact sheet] Accessed 26 November 2007
They are typically loaded into the hearing aid via a rotating battery door, with the flat side (case) as the positive terminal (cathode) and the rounded side as the negative terminal (anode).
These batteries all operate from 1.35 to 1.45 volts.
The type of battery a specific hearing aid utilizes depends on the physical size allowable and the desired lifetime of the battery, which is in turn determined by the Electric power draw of the hearing aid device. Typical battery lifetimes run between 1 and 14 days (assuming 16-hour days).
| { | class=wikitable style="text-align: center; width:100%" | +Hearing Aid Battery Types | |||||||
|---|---|---|---|---|---|---|---|---|---|
| ! style="width:10%;" | Type/ Color Code | ||||||||
| ! style="width:15%;" | Dimensions (Diameter×Height) | ||||||||
| ! style="width:15%;" | Common Uses | ||||||||
| ! style="width:10%;" | Standard Names | ||||||||
| ! style="width:50%;" | Misc Names | ||||||||
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| style="background:blue; color:white;" | 675 | 11.6 mm × 5.4 mm | High-Power Hearing aid#Behind the ear aids (BTE) | BTEs, Cochlear implants | Cochlear Implants | International Electrotechnical Commission | IEC: PR44, ANSI: 7003ZD | 675, 675A, 675AE, 675AP, 675CA, 675CP, 675HP, 675HPX, 675 Implant Plus, 675P (HP), 675PA, 675SA, 675SP, A675, A675P, AC675, AC675E, AC675E/EZ, AC675EZ, AC-675E, AP675, B675PA, B6754, B900PA, C675, DA675, DA675H, DA675H/N, DA675N, DA675X, H675AE, L675ZA, ME9Z, P675, P675i+, PR44, PR44P, PR675, PR675H, PR675P, PR-675PA, PZ675, PZA675, R675ZA, S675A, V675, V675A, V675AT, VT675, XL675, Z675PX, ZA675, ZA675HP | |
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| style="background:orange; color:black;" | 13 | 7.9 mm × 5.4 mm | Hearing aid#Behind the ear aids (BTE) | BTEs, In-the-ear | ITEs | International Electrotechnical Commission | IEC: PR48, ANSI: 7000ZD | 13, 13A, 13AE, 13AP, 13HP, 13HPX, 13P, 13PA, 13SA, 13ZA, A13, AC13, AC13E, AC13E/EZ, AC13EZ, AC-13E, AP13, B13BA, B0134, B26PA, CP48, DA13, DA13H, DA13H/N, DA13N, DA13X, E13E, L13ZA, ME8Z, P13, PR13, PR13H, PR-13PA, PZ13, PZA13, R13ZA, S13A, V13A, VT13, V13AT, W13ZA, XL13, ZA13 | |
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| style="background:brown; color:white;" | 312 | 7.9 mm × 3.6 mm | miniHearing aid#Behind the ear aids (BTE) | BTEs, Hearing aid#Receiver In the Canal/Ear (RIC/RITE) | RICs, Hearing aid#In the canal (ITC), mini canal (MIC) and completely in the canal aids (CIC) | ITCs | International Electrotechnical Commission | IEC: PR41, ANSI: 7002ZD | 312, 312A, 312AE, 312AP, 312HP, 312HPX, 312P, 312PA, 312SA, 312ZA, AC312, AC312E, AC312E/EZ, AC312EZ, AC-312E, AP312, B312BA, B3124, B347PA, CP41, DA312, DA312H, DA312H/N, DA312N, DA312X, E312E, H312AE, L312ZA, ME7Z, P312, PR312, PR312H, PR-312PA, PZ312, PZA312, R312ZA, S312A, V312A, V312AT, VT312, W312ZA, XL312, ZA312 |
| - | |||||||||
| style="background:yellow; color:black;" | 10 | 5.8 mm × 3.6 mm | Hearing aid#In the canal (ITC), mini canal (MIC) and completely in the canal aids (CIC) | CICs, Hearing aid#Receiver In the Canal/Ear (RIC/RITE) | RICs | International Electrotechnical Commission | IEC: PR70, ANSI: 7005ZD | 10, 10A, 10AE, 10AP, 10DS, 10HP, 10HPX, 10SA, 10UP, 20PA, 230, 230E, 230EZ, 230HPX, AC10, AC10EZ, AC10/230, AC10/230E, AC10/230EZ, AC230, AC230E, AC230E/EZ, AC230EZ, AC-230E, AP10, B0104, B20BA, B20PA, CP35, DA10, DA10H, DA10H/N, DA10N, DA230, DA230/10, L10ZA, ME10Z, P10, PR10, PR10H, PR230H, PR536, PR-10PA, PR-230PA, PZA230, R10ZA, S10A, V10, VT10, V10AT, V10HP, V230AT, W10ZA, XL10, ZA10 | |
| - | |||||||||
| style="background:red; color:white;" | 5 | 5.8 mm × 2.1 mm | CICs | International Electrotechnical Commission | IEC: PR63, ANSI: 7012ZD | 5A, 5AE, 5HPX, 5SA, AC5, AC5E, AP5, B7PA, CP63, CP521, L5ZA, ME5Z, P5, PR5H, PR-5PA, PR521, R5ZA, S5A, V5AT, VT5, XL5, ZA5 | |||
| } |