Asymmetric Hearing Aids for Asymmetric Ears?

In a recent American Journal of Audiology study, people with asymmetrical hearing loss didn't express a strong preference for one asymmetric microphone fitting over another in everyday listening situations. Twenty-eight adults with symmetric sensorineural hearing impairment participated in the study; 16 had symmetric hearing-in-noise ability between their right and left ears, and 12 had an asymmetry for speech understanding in noise—a difference of 15 dB, or 20% or greater, on speech understanding scores between ears. The researchers assessed interactions between various microphone fittings and speech signal locations in noise in the laboratory. Additionally, listeners with asymmetry for hearing in noise completed a field trial comparing the two fittings in everyday listening situations. Laboratory testing resulted in different patterns of performance for the two groups. Field trial results revealed that participants generally noticed little difference between the two fittings in daily life. Search "asymmetric" on the American Journal of Audiology website.

Leveling the Hearing Field

By leveling the playing field between hearing devices, future researchers may find it easier to compare the sound quality of devices from a variety of manufacturers. Researchers in the Netherlands applied an inverse filter—a filter that compensates for variations in gain due to individual ear acoustics—to remove differences in frequency response between commercial hearing aids. Researchers increased the similarity of hearing-aid recordings in three steps and used objective quality metric and listening tests to determine whether recordings from different hearing aids were perceptually similar. They found it was not sufficient to manually adjust the hearing-aid insertion gain or to add an additional bandwidth limitation to the recordings. After the application of an inverse filter, however, the perceptual differences between recordings were adequately removed. For more visit the Sage Journals website and search "remove differences."

A Deeper Source of Tinnitus?

Although traditional theories of tinnitus suggest the condition is caused by cochlear damage, a recent study published in the Journal of Neuroscience points to another source—the brain cranking up the volume to account for subtle hearing loss. Researchers focused on 15 participants who reported tinnitus symptoms, as well as 18 participants free of tinnitus, all with normal audiograms. After recording the brain activity of participants as they listened to a series of rapid-fire clicks, researchers found that some sounds showed a reduced amplitude, while sounds generated closer to the brain had normal amplitude—even in those with tinnitus. The authors suggest these results are evidence of "hidden hearing loss," and tinnitus is merely the brain's attempt to compensate by turning up the volume. Search "ringing deeper" at Science News website.