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. on 21 march 2007, the telecommunications industry association issued the tia-1083 standard, which gives manufacturers of cordless telephones the ability to test their products for compatibility with most hearing aids that have a t-coil magnetic coupling mode. with this testing, digital cordless phone manufacturers will be able to inform consumers about which products will work with their hearing aids. the american national standards institute (ansi) has a ratings scale for compatibility between hearing aids and phones: when operating in acoustic (microphone) mode, the ratings are from m1 (worst) to m4 (best). when operating in electromagnetic (telecoil) mode, the ratings are from t1 (worst) to t4 (best). 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: acoustic gain is up to 30 db (with a standard headset); complete invisibility (smartphone is not associated with a hearing aid); ease of use (no need to use additional devices, batteries and so on.); fast switching between the external headset and phone microphone; free distribution of applications. high duration of the battery; high sampling frequency (44.1 khz) providing for excellent sound quality; high wearing comfort; low delay in audio processing (from 6,3 to 15,7 ms – depending on the mobile device model); no loss of settings when switching from one gadget to another and back again; no need to get used to it, when changing mobile devices; user-friendly interface of software settings; it should be clearly understood that "hearing aid" application for smartphone / tablet cannot be considered a complete substitution of a digital hearing aid, since the latter: is a medical device (exposed to the relevant procedures of testing and certification); is adjusted using audiometry procedures. is designed for use by doctor's prescription; functionality of hearing aid applications may involve a hearing test (in situ audiometry) too. however, the results of the test are used only to adjust the device for comfortable working with the application. the procedure of hearing testing in any way cannot claim to replace an audiometry test carried out by a medical specialist, so cannot be a basis for diagnosis. apps such as oticon on for certain ios (apple) and android devices can assist in locating a lost/misplaced hearing aid. wireless recent hearing aids include wireless hearing aids. one hearing aid can transmit to the other side so that pressing one aid's program button simultaneously changes the other aid, so that both aids change background settings simultaneously. fm listening systems are now emerging with wireless receivers integrated with the use of hearing aids. a separate wireless microphone can be given to a partner to wear in a restaurant, in the car, during leisure time, in the shopping mall, at lectures, or during religious services. the voice is transmitted wirelessly to the hearing aids eliminating the effects of distance and background noise. fm systems have shown to give the best speech understanding in noise of all available technologies. fm systems can also be hooked up to a tv or a stereo. 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. oticon hearing aids for use with bluetooth wireless devices phonak wireless fm system in developed countries fm systems are considered a cornerstone in the treatment of hearing loss in children. more and more adults discover the benefits of wireless fm systems as well, especially since transmitters with different microphone settings and bluetooth for wireless cell phone communication have become available. many theatres and lecture halls are now equipped with assistive listening systems 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. directional microphone most older hearing aids have only an omnidirectional microphone. an omnidirectional microphone amplifies sounds equally from all directions. in contrast, a directional microphone amplifies sounds from one direction more than sounds from other directions. this means that sounds originating from the direction the system is steered toward are amplified more than sounds coming from other directions. if the desired speech arrives from the direction of steering and the noise is from a different direction, then compared to an omnidirectional microphone, a directional microphone provides a better signal-to-noise ratio. improving the signal-to-noise ratio improves speech understanding in noise. directional microphones have been found to be the second best method to improve the signal-to-noise ratio (the best method was an fm system, which locates the microphone near the mouth of the desired talker). many hearing aids 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; this can also be helpful during business meetings. 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. telecoil telecoils or t-coils (from "telephone coils") are small devices installed in hearing aids or cochlear implants. an audio induction loop generates an electromagnetic field that can be detected by t-coils, allowing audio sources to be directly connected to a hearing aid. the t-coil is intended to help the wearer filter out background noise. they can be used with telephones, fm systems (with neck loops), and induction loop systems (also called "hearing loops") that transmit sound to hearing aids from public address systems and tvs. in the uk and the nordic countries, hearing loops are widely used in churches, shops, railway stations, and other public places. in the us, telecoils and hearing loops are gradually becoming more common. audio induction loops, telecoils and hearing loops are gradually becoming more common also in slovenia. 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. 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. legislation affecting use in the united states, the hearing aid compatibility act of 1988 requires that the federal communications commission (fcc) ensure that all telephones manufactured or imported for use in the united states after august 1989, and all "essential" telephones, be hearing aid-compatible (through the use of a telecoil). "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 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, 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 and mobile phones used analog technology. audio boot a hearing aid with an audio boot an audio boot or audio shoe is an electronic device used with hearing aids; hearing aids often come with a special set of metal contacts for audio input. typically the audio boot will fit around the end of the hearing aid (a behind-the-ear model, as in-the-ear do not afford any purchase for the connection) to link it with another device, like an fm system or a cellphone or even a digital audio player. direct audio input a dai plug on the end of a cable direct audio input (dai) allows the hearing aid to be directly connected to an external audio source like a cd player or an assistive listening device (ald). by its very nature, dai is susceptible to far less electromagnetic interference, and yields a better quality audio signal as opposed to using a t-coil with standard headphones. an audio boot is a type of device that may be used to facilitate dai. processing every