For healthier hearing aids and happier patients, use a warm-air drying system

Abstract

The first author, an audiologist with Newport Audiology Centers, recently completed a 4-year study on the benefits of patients using the Dry & Store drying system. He and his colleagues found that patients who used the moving warm-air drying system averaged a repair every 27.2 months, while patients who did not averaged a repair every 9.7 months. The researchers expected to see fewer repairs in the group using the drying systems. However, they were surprised to find an almost threefold difference between the two groups. In some cases where the drying kits were not used, they noticed a reduction of 4 to 6 dB in the high-frequency response of recently fitted hearing aids—some as soon as 6 months after the fitting. Doug's findings are consistent with what both of us have experienced in our practices. And, if readers are frustrated with the number of repairs you see, we suggest you recommend warm-air drying systems to your patients. THE ROOT OF THE PROBLEM When moisture and cerumen accumulate in hearing aid microphones and receivers, they cause intermittency, increased distortion, reduction in gain (especially high-frequency), and an overall deterioration of performance. The reduction in gain causes speech to be less clear and reduces word understanding. Eliminating or greatly reducing the moisture in hearing aids allows the instruments to provide high-frequency amplification. The microphones in directional hearing aid systems take a huge amount of abuse from moisture. The directionality of these systems depends on the microphones being perfectly calibrated or very close to it. The microphones must be in phase so the difference in “arrival time” between microphones can be determined. Debris and moisture in microphone screens quickly destroy the mics' function. Using a warm-air drying system helps maintain the effectiveness of directional-microphone systems and reduces the frequency of repairs. WHERE THE MOISTURE COMES FROM The human body is composed primarily of water. We excrete large amounts of moisture from the skin each day. In addition, many people exacerbate the problem by letting water enter and become trapped deep in the ear canal when they are taking a bath or shower. The humidity in and around the ear is high, in the 85%-88% range, and this moisture collects in the microphone, receiver ports, and screens, as well as in the battery and amplifier compartments. When the moist, warm air in the ear canal moves outward toward the cooler metal parts of the hearing aids, it deposits microscopic droplets of water, which accumulate over time. Constant exposure to moisture destroys the integrity of the transducers, causing corrosion or rust in the battery compartment and leading to intermittency or shorts in the amplifier. Moisture and debris also penetrate into the volume control, wreaking further havoc. HOW DEBRIS AND MOISTURE INTERACT We all see lots of debris in the microphone and receiver openings of our patients' hearing aids. This debris is composed of dead skin flakes, lint from clothing, contamination from hair and skin products, and other miscellaneous material. The debris absorbs moisture like a sponge. When a wearer removes his or her hearing aids for the night, a sufficient amount of the moisture in the debris usually evaporates that the hearing aids work the next morning. But, as soon as they are placed in (or on) the ears the next morning, the debris at the entrance to the microphone or exit port of the receiver begins absorbing moisture again, resulting either in gain being reduced or amplification stopping altogether. When hearing aids are sent in for repair, the damaged and moisture-laden transducers are usually replaced. Often they feed back when they are refitted on the patient. This occurs because the repaired instruments are providing considerably more amplification in the higher frequencies now that the microphones and receivers are working correctly. BENEFITS OF A DRYING SYSTEM We have found that using moisture-absorbing products such as the Dry & Store offers many benefits, including: greater gain, especially in the crucial high frequencies, clearer sound quality, improved word understanding, including in noise, better localization of sound, reduced need for repairs, less irritation to the ear canal because the UV light in the system kills spores, bacteria, and fungi, a 5%-10% increase in battery life, and fewer patient complaints. In our practices, we urge our patients to purchase and use a warm-air drying system. We recommend that you do so too.