3.7. While different types of hearing aids exist in the market, specific hearing aids appropriate for the L.M.I.C. context are described by the W.H.O. P.P.P..

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3.7. While different types of hearing aids exist in the market, specific hearing aids appropriate for the L.M.I.C. context are described by the W.H.O. P.P.P..

Hearing aids are not one size fits all, and are differentiated by amplification power (the more severe the hearing loss, the higher the amplification power required), amplification technology (analogue vs. digital), sound processing capabilities, style (refer to Table 3 on hearing aid styles), battery types used, and special features (such as Bluetooth, Artificial Intelligence, etc.). Telecoil facility and compatibility39, direct audio input, directional microphones, etc. are also important functions of hearing aids that are necessary for long-term optimal use in various settings.

TABLE 3: EXAMPLES OF HEARING AID STYLES 40

BODY WORN BEHIND-THE-EAR (B.T.E.) W.H.O. P.P.P. recommended RECEIVER-IN-CANAL (R.I.C.) IN-THE-EAR COMPLETELY-IN-THE-CANAL/INVISIBLE-IN-THE-CANAL
Photo of a body worn hearing device, which includes a regtangular receiver that is attached to the body and a pair of headphones that are attached to the receiver.
Image of a silver, behind the ear hearing aid
Photo of a silver, Micro Receiver-In-Canal Hearing Aid. Looks similar to the behind the ear hearing aid, but the receiver is attached to a larger piece in the ear canal.
Image of in-the-ear hearing aid of skin colored and a custom shape to fit in the ear.
Image of completely-in the canal hearing aid that is made of skin colored and has clear components and is shaped to fit completely in ear.
Least complex hearing aids that can be worn on the user's body with earbuds placed in the ear. The technology is housed in a casing that rests behind the ear and a plastic, acoustical tube directs sound into an earbud or custom earmould. R.I.C.s are a subset of B.T.E. hearing aids where the receiver of the hearing aid is inside the ear canal. Custom designed hearing aids that are complex to fit and require significant care. They are visible as they sit on the outer ear of the user. Custom made to fit completely in the ear canal with only a small plastic ‘handle’ on the outside for removing it when not in use.

The W.H.O. P.P.P. recommends Behind-the-Ear (B.T.E.) hearing aids as the primary choice for public health distribution in L.M.I.C. as it has the widest coverage range for severity levels and is the easiest to fit among current styles.

Many hearing aids are able to serve multiple levels of severity, but not all levels. Table 4 provides rough estimates of the mix of devices that would be required to meet the needs of a population. However, the W.H.O. P.P.P. does not specify the mix of products, based on amplification power of user needs that should be procured by hearing programs or procurement agents to meet the population's needs. Hearing aids should be selected to meet the amplification and perceptive needs of the user. The P.P.P. is also limited by the fact that it does not outline a target price for the total cost of ownership over the lifetime of the product nor does it support additional technical guidance for procurement. Additional limitations are covered in the next section on quality.

TABLE 4: ROUGH ESTIMATION OF THE PROPORTION OF DEVICES NEEDED IN L.M.I.C.S 41

HEARING LOSS SEVERITY MILD MODERATE SEVERE PROFOUND
Recommended proportion 10% 45% 35% 10%

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3.6. W.H.O. global guidelines related to hearing aid provision in low-resource settings (L.R.S.) are outdated and lack specificity, which has led to a variety of approaches to hearing aid provision.  Home | ToC 3.8. No global standard for quality testing currently exists to differentiate quality hearing aids from poor quality products.