First Person Report: Not Everyone Can Adjust to Digital Hearing Aids After A Lifetime Of Analog(ue) ~New post in The Hearing Blog (Also, see first comment) Longtime UK hearing aid user Karen Stockton passionately describes in The Limping Chicken how what looks good on paper, namely that of enhancing audibility of sounds with the wide dynamic range compression (WDRC; technically logarithmic gain) found on digital hearing aids, does not work for the profoundly deaf whose broken ears have cochlear dead zones as they rely on speech envelope detection, namely those whose auditory system between their outer hair cells and dorsal cochlear nuclei lack the temporal resolution to resolve the fine structure of speech. The reason: WDRC actually squashes the speech envelope, destroying the ability for the auditory cortex to decode that crucial information transmitted from the cochlear nuclei; and when this information is lost, as will be explained below, disastrous results can and will occur. When you read Karens story, youll note the condescension, bordering on arrogance, of her audiologists, with their we know whats best for you attitudes. Whats more, weve seen these attitudes festering on both sides of the Atlantic, as improperly trained, button-pushing hearing aid professionals are just chimping it by plugging the audiogram into the fitting software, clicking Autofit… And then ignoring the patient complaints, because they dont understand the fundamentals of speech signal synthesis and detection. This is the second article in our series on speech envelope preservation, the first being Speech Envelope Detection vs AGC Attack & Release in Hearing Aids, which both lays out the problem, and more importantly, provides the precise, elegant solution. thehearingblog/archives/2689
Posted on: Sun, 10 Aug 2014 19:03:28 +0000
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