[HD-11] (1997)Introduced in 1997, the HD-11 was distinct from other digital hearing aid models, a frequency-compression type digital hearing aid developed for those with profound hearing loss whose hearing remains only in the low frequency range. With frequency compression, the higher frequency sounds are converted into the audible frequency range. Later, more digital hearing aid models for the profoundly and severely hearing impaired were developed in BTE and ITE types and introduced as products like the HI-G7, Rionet PIXY, and HB-W1 types. Rion markets the world’s rst digital hearing aidIn 1948, Rion introduced the first domestic mass-produced hearing aid. Since then, with the development of various products, Rion has set the pace for hearing aid progress in Japan. Among the major technological turning points was the digitalization of hearing aids in the late 1980s.The transition from analog to digital was occurring with many products at the time. With the creation of a prototype of a digital hearing aid at a US university, this wave of digitalization had begun impinging on the hearing aid industry. In September 1991, against this backdrop, Rion introduced the HD-10, the world’s first body-type digital hearing aid.“We knew that there was no point making digital hearing aids unless we could adopt a sound processing method not available with conventional analog devices,” recalls Makoto Tateno. At the time, there were more BTE (behind-the-ear) models available on the market than body-type models. But the smaller the device, the more constraints there are on design and manufacture in terms of voltage and power.“A hearing aid that offers digital-only functions would attract users even if it wasn’t a BTE type,” thought Tateno and his team.Of course, the process of producing the first of anything in the world can’t be expected to be free of challenges. The development of the HD-10 entailed numerous trials and errors.In digital hearing aids, sound input through the microphone is converted into digital signals using an AD (analog-to-digital) converter. The signal is then processed by a DSP and converted back into an analog signal to be output as sound. Tateno recalls how hard it was to procure ICs (integrated circuits), DSPs, and AD converters for the development of the HD-10. “We had a limited budget, so we couldn’t develop an optimal IC from scratch. That’s why we looked into IC products known as standard cells—which are sort of semi-custom-made ICs. We were trying to find an affordable one we could use in a hearing aid, given our budget.”The most challenging part was selecting the AD converter, Tateno adds. Hearing aids have to be capable of working under various conditions in which the loudness and the distance to the sound source vary. The team repeated many trial and error processes using various AD converters.Ultimately, for the HD-10, they settled on a standard cell equipped with an AD converter with performance sufficient for hearing aids. Looking back Tateno identifies the discovery of that IC as a major breakthrough.[HD-10] (1991)The HD-10 was the world’s rst digital hearing aid marketed in 1991. The input sound was divided into three ranges before digital conversion: low, middle and high frequency ranges. This allowed separate signal processing for each frequency range and provided freedom in controlling the I/O char-acteristics compared to conventional analog hearing aids. The model also stored several sound settings to allow users to switch between them with a press of a button according to the situation.[HI-P1K] (1997)Development of digital hearing aids continued after the marketing of the HD-10, despite the difculties in procuring DSPs specially designed for hearing aids. The HI-P1K was a custom-made programmable digital hearing aid in-troduced in 1997. While an analog circuit was used for the sound processing, digital processing was employed for switching between different sound set-tings according to the situation. The model stands out among other hearing aids of this period of transition from analog to digital.8
元のページ ../index.html#10