| ESSENTIAL & DESIRABLE FEATURES | REQUIREMENT | |
| Type of hearing aids | Hearing Aid Format | Behind-the-ear, with accompanying earmoulds, are preferred to body-worn or in-the-ear devices. They provide greater ease of fit, are less prone to malfunctioning and only the earmould needs to be replaced due to growth. Should be of appropriate size and shape for the user's ear and can be securely fitted behind the ear. |
| Digital technology | Digital technology is standard in H.I.C.s and offers advantages over analogue sound processing. Allows greater flexibility in shaping the output signal to accommodate a wide rand of hearing loss configurations and permits better use of residual hearing | |
| Performance requirements | The Profile provides the minimum electroacoustic performance requirement parameters for manufacturing hearing aids including: maximum output sound pressure level, maximum full-on acoustic gain, basic frequency response, total harmonic distortion at 70 d.B. SPL input, equivalent input noise at 1 k.H.z., battery current drain, battery life, and telecoil sensitivity. | |
| Prescription-based amplification | The fitting of hearing aids should follow an evidence-based prescription formula method that calculates the amount of amplification appropriate for the degree of hearing loss. Hearing threshold-based prescription procedures are preferred. | |
| Robust design | Hearing aids should be designed to withstand mild impact shocks, light rain showers and dust, and should provide at least five years' continuous usage. | |
| Hearing Aid Features | Compression | Some form of compression is required for wearer comfort and optimal intelligibility. Compression prevents loud amplification of higher-intensity sounds, preventing amplification-induced hearing loss, and allows higher amplification of soft noises. |
| Feedback Management | Feedback management reduces the feedback loop (whistling) that occurs in hearing aids. It is often the result of loose or ill-fitting custom or non-custom earmoulds, which are common in L.M.I.C.s. An added stable gain, the measure of additional amplification available when feedback management is activated, of 10 d.B. is recommended. | |
| On/off switch | A dedicated on–off switch or simple alternative means of powering down is required to facilitate user management of the hearing aid and battery conservation. | |
| Volume control | A user-directed control to manage volume amplification of the hearing aid is required. The volume control should have a range of at least 30d.B. and be clearly numbered | |
| Adaptive noise reduction | Adaptive noise reduction systems are a desirable feature and improve ease of listening in situations where significant background noise is present. | |
| Climate resistance | The potential for humidity-related damage can be reduced by “tropicalizing” hearing aids during manufacture, using spray- or dip-applied coatings of water-repellent materials. Liquid-repellent nano-coatings that can be applied to all hearing-aid components at the molecular level, resulting in high resistance to water (and oil and wax) are desirable. Use of water-repellent fabric for the microphone inlet port and of waterproof membranes for receivers and battery compartments is also desirable. | |
| Telecoil facility | A telecoil is a small copper coil that allows the hearing aid to detect an electromagnetic induction signal. It picks up the signal from a compatible telephone or other electromagnetic looped systems, enabling their use. This is a desirable feature. | |
| Direct Audio Input | Direct audio input allows a hearing aid to be attached to other audio equipment, such as a cellular or landline telephone, M.P.3 player, television, microphone or F.M. wireless receiver and is desirable. | |
| Low-battery alert | An audio signal to alert the user to the need to replace a battery is a desirable feature. | |
| Other Characteristics | Affordability | As cost is a key barrier to uptake, hearing aids must be affordable. Efforts should be made to ensure that bulk purchases can be made at favourable prices from manufacturers and that government policy does not inflate consumer costs. |
| Hearing-aid labelling | Each hearing aid should be permanently marked with the name of the manufacturer or distributor, the model name, serial number and year of manufacture and a “+” symbol to indicate location of positive terminal for battery. | |
| Hearing-aid packaging | Packaging, and the associated labelling, should be able to withstand exposure to excessive moisture and other impacts associated with the long distribution chain and ensure safe storage. Packaging should include technical specifications, contraindications and user guide with clear instructions in the national language. | |
| Power supply | Hearing aids should be designed to accept a battery type that is readily obtainable in the local region. Batteries should be clearly labelled and difficult for children to open. Rust resistant and/or rechargeable battery systems are desirable, but not essential. | |
| Appropriate earmoulds | Earmoulds should be compatible with the type of hearing aid, device gain/output, and user requirements. Various options may be satisfactory, including stock earmoulds (pre-configured), custom earmoulds, instant earmould products, and disposable standard flexible dome moulds. Custom earmoulds are desirable but often sustainable production facilities are not available and therefore non-custom dome earmoulds are preferred for L.M.I.C.s. | |
| Hearing aid repair | Hearing aid housing should be able to be opened for maintenance purposes and to allow preset controls (if provided) to be adjusted without risk of damage to the housing or internal components. Facilities must be available for minor repairs such as device cleaning, replacement of earhooks, adjustments of battery contacts, changing of switches, and trimmer and volume controls. |
The full W.H.O. Preferred Profile can be accessed at: https://apps.who.int/iris/rest/bitstreams/1087770/retrieve