The first hearing aid was created in the 17th century. The movement toward modern hearing aids began with the creation of the telephone, and the first electric hearing aid was created in 1898. By the late 20th century, the digital hearing aid was distributed to the public commercially. Some of the first hearing aids were external hearing aids. External hearing aids direct sounds in front of the ear and block all other noises. The apparatus would fit behind or in the ear.
The invention of the carbon microphone, transmitters, digital signal processing chip or DSP, and the development of computer technology helped transform the hearing aid to its present form.[1]
Frederick Rein's acoustic chair, designed for King John VI of Portugal in the early 19th-century.
The use of ear trumpets for the partially deaf, dates back to the 17th century.[1] By the late 18th century, their use was becoming increasingly common. Collapsible conical ear trumpets were made by instrument makers on a one-off basis for specific clients. Well-known models of the period included the Townsend Trumpet (made by the deaf educator John Townshend), the Reynolds Trumpet (specially built for painter Joshua Reynolds) and the Daubeney Trumpet.
The first firm to begin commercial production of the ear trumpet was established by Frederick C. Rein in London in 1800. As well as producing ear trumpets, Rein also sold hearing fans, and speaking tubes. These instruments helped amplify sounds, while still being portable. However, these devices were generally bulky and had to be physically supported from below. Later, smaller, hand-held ear trumpets and cones were used as hearing aids.[2][3]
Frederick Rein Ltd.'s catalog, displaying evolving 19th century designs.
Rein was commissioned to design a special acoustic chair for the ailing King John VI of Portugal in 1819. The throne was designed with ornately carved arms that looked like the open mouths of lions. These holes acted as the receiving area for the acoustics, which were transmitted to the back of the throne via a speaking tube, and into the king's ear.[4] Finally in the late 1800s, the acoustic horn, which was a tube that had two ends, a cone that captured sound, and was eventually made to fit in the ear.[1]
Toward the late 19th century, hidden hearing aids became increasingly popular. Rein pioneered many notable designs, including his 'acoustic headbands', where the hearing aid device was artfully concealed within the hair or headgear. Reins' Aurolese Phones were headbands, made in a variety of shapes, that incorporated sound collectors near the ear that would amplify the acoustics. Hearing aids were also hidden in couches, clothing, and accessories. This drive toward ever increasing invisibility was often more about hiding the individual's disability from the public than about helping the individual cope with his or her problem.[3]
Electronic hearing aids
A 1933 ad for early vacuum tube hearing aids.These German hearing aids date from around 1920 to 1950. They include an attachment similar to a telephone receiver. Museum of Medicine, Berlin, Germany.
The first electronic hearing aids were constructed after the invention of the telephone and microphone in the 1870s and 1880s. The technology within the telephone increased how acoustic signals could be altered. Telephones were able to control the loudness, frequency, and distortion of sounds. These abilities were used in the creation of the hearing aid.[3]
The first electric hearing aid called the Akouphone, was created by Miller Reese Hutchison in 1898. It used a carbon transmitter, so that the hearing aid could be portable. The carbon transmitter was used to amplify sound by taking a weak signal and using electric current to make it a strong signal.[3] These electronic hearing aids could eventually be shrunk into purses and other accessories.[3]
One of the first manufacturers of the electronically amplified hearing aid was the Siemens company in 1913. Their hearing aids were bulky and not easily portable. They were about the size of a "tall cigar box" and had a speaker that would fit in the ear.[1]
The first vacuum tube hearing aid was patented by a Naval engineer Earl Hanson in 1920. It was called the Vactuphone and used the telephone transmitter to turn speech into electrical signals. After the signal was converted, it would be amplified when it moved to the receiver. The hearing aid weighed seven pounds, which made it light enough to be carried.[3]Marconi in England and Western Electric in the US began marketing vacuum tube hearing aids in 1923.
During the 1920s and 1930s, the vacuum tube hearing aid became more successful and began to decrease in size with better miniaturization techniques. The Acousticon's Model 56 was created in the mid-1920s and was one of the first portable hearing aid units, although it was quite heavy.[1] The first wearable hearing aid using vacuum tube technology went on sale in England in 1936, and a year later in the United States.[5] By the 1930s, hearing aids were becoming popular to the public.[3]Multitone of London patented the first hearing aid to use automatic gain control. The same company introduced a wearable version in 1948.[1]
Military technological advances that occurred in World War II helped the development of hearing aids. One of the major advances that World War II enabled was the idea of miniaturization.[3] This could be seen by Zenith's pocket-sized Miniature 75.[1]
Transistor hearing aids
This early 1980s photo shows a hearing aid with a transistor that is worn over the chest with shoulder straps. It would sometimes have a problem with static interference, even if the wearer laughed or smiled.
The development of transistors in 1948 by Bell Laboratories led to major improvements to the hearing aid.[3] The transistor was invented by John Bardeen, Walter Brattain, and William Shockley. Transistors were created to replace vacuum tubes; they were small, required less battery power and had less distortion and heat than their predecessor.[3] These vacuum tubes were typically hot and fragile, so the transistor was the ideal replacement.[6] The 1952 Sonotone 1010 used a transistor stage along with vacuum tubes, to extend battery life. The size of these transistors led to developments in miniature, carbon microphones. These microphones could be mounted on various items, even eyeglasses.[3] In 1951, Raytheon manufactured the transistor and was one of the first companies to mass-produce transistors to throughout America. Raytheon realized that their hearing aid only lasted short-term and began to sell the vacuum-tube hearing aids again along with transistor hearing aids.[3]
The act of putting transistors into hearing aids was so quick that they were not properly tested. It was later found that transistors could get damp. Because of this dampness, the hearing aid would only last for a few weeks and then die. In order to stop this from happening, a coating had to be put on the transistor to protect it from dampness. This problem had to be fixed in order for transistors in hearing aids to be successful.[6]
Zenith was the first company to realize the problem with transistors was the body heat of individuals. After coming to this conclusion, the first "all-transistor" hearing aids were offered in 1952, called the Microtone Transimatic and the Maico Transist-ear. In 1954, the company, Texas Instruments, produced a silicon transistor, which was much more effective than the previous version.[3] The end of the transistor was marked by the creation of the integrated circuit or IC by Jack Kilby at Texas Instruments in 1958 and the technique was perfected in hearing aids over the next 20 years.[3]
Elmer V. Carlson, the author of thirty patents, was instrumental in inventing many of the components of the modern hearing aid.[7][8]
Digital hearing aid
Beginning in the early 1960s, Bell Telephone Laboratories created digital processing for creating both speech and audio signals on a large mainframe computer. Because of the slow processing ability of these large digital computers of the era, the process of simulating hearing aids was extremely slow. The processing of the audio speech signal took longer than the length of the duration of the speech signal itself preventing the processing of speech in real time. This made it nearly impossible to conceive the idea that a self-contained, wearable digital hearing aid could be made small enough to fit onto an ear like a conventional analog hearing aid. However, this digital processing research was important for learning about how to develop sounds for those with hearing disabilities.[2]
In the 1970s, the microprocessor was created. This microprocessor helped to open up the door to miniaturization of the digital hearing aid.[3] Moreover, researcher Edgar Villchur developed an analog multi-channel amplitude compression device with amplitude compression that enabled the audio signal to be separated into frequency bands. These frequency bands were able to adjust the analog sound non-linearly so that loud sounds could be less amplified and weak sounds could become more amplified. The system of multi-channel amplitude compression would be later used as the fundamental structural design for the first hearing aids that used digital technology.[2]
Also in the 1970s the creation of a hybrid hearing aid was possible in which the analog components of a conventional hearing aid consisting of amplifiers, filters and signal limiting were combined with a separate digital programmable component into a conventional hearing aid case. The audio processing remained analog but was able to be controlled by the digital programmable component. The digital component could be programmed by connecting the device to an external computer in the laboratory then disconnected to allow the hybrid device to function as a conventional wearable hearing aid.
The hybrid device was effective from a practical point of view because of the low power consumption and compact size. At that time, low-power analog amplifier technology was well developed in contrast to the available semiconductor chips able to process audio in real time. The combination of high performance analog components for real time audio processing and a separate low power digital programmable component only for controlling the analog signal led to the creation several low power digital programmable components able to implement different types of digital control of analog circuits.
A hybrid hearing aid was developed by Etymotic Design. A little later, Mangold and Lane[9] created a programmable multi-channel hybrid hearing aid. Graupe[10] with co-authors developed a digital programmable component that implemented an adaptive noise filter that could be added to a hybrid hearing aid, referred to as the Zeta Noise Blocker, routinely adjusted the gain in the frequency channels to help control high levels of noise. The chip was integrated in a number of hearing aids in the 1980s.[11]
The creation of high-speed digital-array processors used in minicomputers opened up the door for advances in full digital hearing aids.[1] These minicomputers were able to process audio signals at speeds that were equivalent to real-time. In 1982, at the City University of New York, a real-time full digital experimental hearing aid was created based on the digital array processor in an external, standalone minicomputer and an FM radio transmitter that allowed a wireless connection between the minicomputer and individual wearing a transmitter on the body. The FM transmitter on the body was connected by a wire to an ear microphone and loudspeaker. Technically this was a wearable hearing aid though it was not self contained and the range the user could use it was limited by the range of the wireless connection and the external minicomputer was extremely heavy and nearly impossible to move[2]
Oticon hearing aids to be used with Bluetooth wireless devices.
preventing it from being used as conventional hearing aid in real world environments. However, this was a major breakthrough in the creation of a full digital hearing aid.
Also in the early 1980s a research group at Central Institute for the Deaf headed up by faculty members at Washington University in St. Louis MO created the first full digital wearable hearing aid.[12][13] They first conceived a complete, comprehensive full digital hearing aid, then designed and fabricated, miniaturized full digital computer chips using custom digital signal processing chips with low power and very large scale integrated (VLSI) chip technology able to process both the audio signal in real time and the control signals yet able to be powered by a battery and be fully wearable as a full digital wearable hearing aid able to be actually used by individuals with hearing loss in any environment similar to a conventional hearing aid. Engebretson, Morley and Popelka were the inventors of the first full digital hearing aid. Their work resulted in US Patent 4,548,082, "Hearing aids, signal supplying apparatus, systems for compensating hearing deficiencies, and methods" by A Maynard Engebretson, Robert E Morley Jr. and Gerald R Popelka, filed in 1984 and issued in 1985. This full digital wearable hearing aid also included many additional features now used in all contemporary full digital hearing aids including a bidirectional interface with an external computer, self-calibration, self-adjustment, wide bandwidth, digital programmability, a fitting algorithm based on audibility, internal storage of digital programs, and fully digital multichannel amplitude compression and output limiting. This group created several of these full digital hearing aids and used them for research on hearing impaired people as they wore them in the same manner as conventional hearing aids in real-world situations. In this first full DHA all stages of sound processing and control were carried out in binary form. The external sound from microphones positioned in an ear module identical to a BTE was first converted into binary code, then digitally processed and digitally controlled in real time, then converted back to an analog signal sent to miniature loudspeakers positioned in an ITE ear module. These specialized hearing aid chips continued to become smaller, increase in computational ability and require even less power. Now, virtually all commercial hearing aids are fully digital and their digital signal processing capability has significantly increased. Very small and very low power specialized digital hearing aid chips are now used in all hearing aids manufactured worldwide. Many additional new features also have been added with various on-board advanced wireless technology.[14]
Commercial digital chips that were devoted to high-speed digital signal processing or DSP became available in 1982. The first commercial full digital hearing aid using a commercial DSP chip was created in 1987 by the Nicolet Corporation. The hearing aid contained a body-worn processor that had a hardwire connection with an ear mounted transducer. While the Nicolet Corporation's hearing aid was not publicly successful and the company shortly folded, it was able to start a competition among hearing aid manufacturers to create more effective full digital hearing aids. Two years later, in 1989, the commercial behind-the-ear (BTE) full digital hearing aid was launched.[2] One of the major contributions of these chips was the ability to process both speech and other types of noises in real time. One major down fall of these chips was that they were massive and used up a lot of battery charge, which made them nearly impossible to be worn.
In addition to the Nicolet Corporation, Bell Laboratories expanded upon the hearing aid business by developing a hybrid digital-analog hearing aid. This hearing aid used digital circuits to handle a two-channel compression amplifier. Even though early research on this hearing aid was successful, AT&T, the parent company to Bell Laboratories, pulled out of the hearing aid market and sold its rights to Resound Corporation in 1987. When the hybrid hearing aid was put on in the market, it helped bring major changes to the world of the hybrid hearing aid.[2]
After the success of the Resound Corporation, other hearing aid manufacturers began putting out hybrid hearing aids that included analog amplifiers, filters, and limiters that were managed digitally. There were many benefits to these hearing aids that included storing parameter settings, having a capability for paired-comparison testing, having settings for different acoustic environments, and having more advanced methods of signal processing that included multi-channel compression.[2]
The next major milestone was creating a commercial full digital hearing aid. The Oticon Company developed the first commercial full digital hearing aid in 1995, but it was only distributed to audiological research centers for research on digital technology in the realm of acoustic amplification. The Senso was the first commercially successful, full digital hearing aid, and was created by Widex in 1996. After the success of the Senso, Oticon began marketing their own hearing aid, the DigiFocus.[2]
Current digital hearing aids are now programmable which enables digital hearing aids to regulate the sound on their own, without using a separate control. The full digital hearing aid can now adjust itself depending on what environment it is in and often does not even need a physical volume control button.[15]
Recently, "Made for iPhone hearing aids" (MFi) were introduced by Resound, which enables users of MFi digital hearing aids to stream phone calls, music, and podcasts directly from iOS devices.[16]
Directly leveraging the audio processing power potential in smartphones, Jacoti BVBA from Belgium developed ListenApp, the first digital hearing aid application to win CE certification and FDA approval as a medical device.[17]
Electronics is a scientific and engineering discipline that studies and applies the principles of physics to design, create, and operate devices that manipulate electrons and other electrically charged particles. Electronics is a subfield of physics and electrical engineering which uses active devices such as transistors, diodes, and integrated circuits to control and amplify the flow of electric current and to convert it from one form to another, such as from alternating current (AC) to direct current (DC) or from analog signals to digital signals.
An amplifier, electronic amplifier or (informally) amp is an electronic device that can increase the magnitude of a signal. It is a two-port electronic circuit that uses electric power from a power supply to increase the amplitude of a signal applied to its input terminals, producing a proportionally greater amplitude signal at its output. The amount of amplification provided by an amplifier is measured by its gain: the ratio of output voltage, current, or power to input. An amplifier is defined as a circuit that has a power gain greater than one.
An integrated circuit (IC), also known as a microchip, computer chip, or simply chip, is a small electronic device made up of multiple interconnected electronic components such as transistors, resistors, and capacitors. These components are etched onto a small piece of semiconductor material, usually silicon. Integrated circuits are used in a wide range of electronic devices, including computers, smartphones, and televisions, to perform various functions such as processing and storing information. They have greatly impacted the field of electronics by enabling device miniaturization and enhanced functionality.
Headphones are a pair of small loudspeaker drivers worn on or around the head over a user's ears. They are electroacoustic transducers, which convert an electrical signal to a corresponding sound. Headphones let a single user listen to an audio source privately, in contrast to a loudspeaker, which emits sound into the open air for anyone nearby to hear. Headphones are also known as earphones or, colloquially, cans. Circumaural and supra-aural headphones use a band over the top of the head to hold the drivers in place. Another type, known as earbuds or earpieces, consists of individual units that plug into the user's ear canal. A third type are bone conduction headphones, which typically wrap around the back of the head and rest in front of the ear canal, leaving the ear canal open. In the context of telecommunication, a headset is a combination of a headphone and microphone.
A mixing console or mixing desk is an electronic device for mixing audio signals, used in sound recording and reproduction and sound reinforcement systems. Inputs to the console include microphones, signals from electric or electronic instruments, or recorded sounds. Mixers may control analog or digital signals. The modified signals are summed to produce the combined output signals, which can then be broadcast, amplified through a sound reinforcement system or recorded.
A megaphone, speaking trumpet, bullhorn, blowhorn, or loudhailer is usually a portable or hand-held, cone-shaped acoustic horn used to amplify a person's voice or other sounds and direct it in a given direction. The sound is introduced into the narrow end of the megaphone, by holding it up to the face and speaking into it, and the sound waves radiate out the wide end. A megaphone increases the volume of sound by increasing the acoustic impedance seen by the vocal cords, matching the impedance of the vocal cords to the air, so that more sound power is radiated. It also serves to direct the sound waves in the direction the horn is pointing. It somewhat distorts the sound of the voice because the frequency response of the megaphone is greater at higher sound frequencies.
A hearing aid is a device designed to improve hearing by making sound audible to a person with hearing loss. Hearing aids are classified as medical devices in most countries, and regulated by the respective regulations. Small audio amplifiers such as personal sound amplification products (PSAPs) or other plain sound reinforcing systems cannot be sold as "hearing aids".
A mixed-signal integrated circuit is any integrated circuit that has both analog circuits and digital circuits on a single semiconductor die. Their usage has grown dramatically with the increased use of cell phones, telecommunications, portable electronics, and automobiles with electronics and digital sensors.
Plantronics, Inc. is an American electronics company — branded Poly to reflect its dual Plantronics and Polycom heritage — producing audio communications equipment for business and consumers. Its products support unified communications, mobile use, gaming and music. Plantronics is headquartered in Santa Cruz, California, and most of its products are produced in China and Mexico.
An electronic component is any basic discrete electronic device or physical entity part of an electronic system used to affect electrons or their associated fields. Electronic components are mostly industrial products, available in a singular form and are not to be confused with electrical elements, which are conceptual abstractions representing idealized electronic components and elements. A datasheet for an electronic component is a technical document that provides detailed information about the component's specifications, characteristics, and performance.
An ear trumpet is a tubular or funnel-shaped device which collects sound waves and leads them into the ear. They are used as hearing aids, resulting in a strengthening of the sound energy impact to the eardrum and thus improved hearing for a deaf or hard-of-hearing individual. Ear trumpets were made of sheet metal, silver, wood, snail shells or animal horns. They have largely been replaced in wealthier areas of the world by modern hearing aid technology that is much smaller and less obtrusive, albeit more expensive.
The carbon microphone, also known as carbon button microphone, button microphone, or carbon transmitter, is a type of microphone, a transducer that converts sound to an electrical audio signal. It consists of two metal plates separated by granules of carbon. One plate is very thin and faces toward the speaking person, acting as a diaphragm. Sound waves striking the diaphragm cause it to vibrate, exerting a varying pressure on the granules, which in turn changes the electrical resistance between the plates. Higher pressure lowers the resistance as the granules are pushed closer together. A steady direct current is passed between the plates through the granules. The varying resistance results in a modulation of the current, creating a varying electric current that reproduces the varying pressure of the sound wave. In telephony, this undulating current is directly passed through the telephone wires to the central office. In public address systems it is amplified by an audio amplifier. The frequency response of most carbon microphones, however, is limited to a narrow range, and the device produces significant electrical noise.
Adaptive feedback cancellation is a common method of cancelling audio feedback in a variety of electro-acoustic systems such as digital hearing aids. The time varying acoustic feedback leakage paths can only be eliminated with adaptive feedback cancellation. When an electro-acoustic system with an adaptive feedback canceller is presented with a correlated input signal, a recurrent distortion artifact, entrainment is generated. There is a difference between the system identification and feedback cancellation.
A direct-coupled amplifier or DC amplifier is a type of amplifier in which the output of one stage of the amplifier is coupled to the input of the next stage in such a way as to permit signals with zero frequency, also referred to as direct current, to pass from input to output. This is an application of the more general direct coupling. It was invented by Harold J Paz and Francis P. Keiper Jr. in 1955. It displaced the triode vacuum tube amplifier designed by Lee de Forest. Almost all vacuum tube circuit designs are now replaced with direct coupled transistor circuit design. It is the first transistor amplifier design that did not include coupling capacitors. The direct-coupled amplifier allowed analog circuits to be built smaller with the elimination of coupling capacitors and removed the lower frequency limitation that is dependent on capacitors.
A contralateral routing of signals (CROS) hearing aid is a type of hearing aid that is used to treat a condition in which the patient has no usable hearing in one ear and minimal hearing loss or normal hearing in the other ear. This is referred to as single sided deafness.
An electronic circuit is composed of individual electronic components, such as resistors, transistors, capacitors, inductors and diodes, connected by conductive wires or traces through which electric current can flow. It is a type of electrical circuit. For a circuit to be referred to as electronic, rather than electrical, generally at least one active component must be present. The combination of components and wires allows various simple and complex operations to be performed: signals can be amplified, computations can be performed, and data can be moved from one place to another.
Electric acoustic stimulation (EAS) is the use of a hearing aid and a cochlear implant technology together in the same ear. EAS is intended for people with high-frequency hearing loss, who can hear low-pitched sounds but not high-pitched ones. The hearing aid acoustically amplifies low-frequency sounds, while the cochlear implant electrically stimulates the middle- and high-frequency sounds. The inner ear then processes the acoustic and electric stimuli simultaneously, to give the patient the perception of sound.
Miracle-Ear, Inc. is a hearing aid and hearing care company consisting of a network of franchised and corporately owned retail locations. The company is a subsidiary of Amplifon, the worldwide leader in hearing care and hearing aid retail based in Milan, Italy. Miracle-Ear's U.S. headquarters are located in Minneapolis, Minnesota. As of 2023 it has more than 1,500 locations in the United States, and it is the best-known hearing aid brand in the U.S.
SoundBite Hearing System is a non-surgical bone conduction prosthetic device that transmits sound via the teeth. It is an alternative to surgical bone conduction prosthetic devices, which require surgical implantation into the skull to conduct sound.
Personal Sound Amplification Products, also known as "Personal Sound Amplification Devices," or by the acronym PSAP, are defined by the U.S. Food and Drug Administration as wearable electronic products that are intended to amplify sounds for people who are not Deaf or Hard of Hearing. They are not hearing aids, which the FDA describes as intended to compensate for hearing loss. According to Dr. Mann of the FDA, choosing a PSAP as a substitute for a hearing aid can lead to more damage to your hearing.
References
1 2 3 4 5 6 7 8 Howard, Alexander (November 26, 1998). "Hearing Aids: Smaller and Smarter". New York Times.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Mills, Mara. "Hearing Aids and the History of Electronics Miniaturization." IEEE Annals of the History of Computing 33.2 (2011): 24-44.
↑ Levitt, H (December 26, 2007). "Digital hearing aids: wheelbarrows to ear inserts". ASHA Leader. 12 (17): 28–30.
↑ Engebretson, AM, Popelka, GR, Morley, RE, Niemoeller, AF, and Heidbreder, AF: A digital hearing aid and computer-based fitting procedure. Hearing Instruments 1986; 37(2): 8-14
↑ Popelka, GR: Computer assisted hearing aid fitting, in Microcomputer Applications in Rehabilitation of Communication Disorders, M.L. Grossfeld and C.A. Grossfeld, Editors. 1986, Aspen Publishing: Rockville, Maryland. 67-95
↑ Popelka, GR., Moore, BJC, Popper, AN, and Fay, RR: 2016, Hearing Aids, Springer Science, LLC, New York
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