2005 Fiscal Year Final Research Report Summary
Assessment of a public address system for assisting listening in hearing impaired persons.
| Project/Area Number |
16500339
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Rehabilitation science/Welfare engineering
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| Research Institution | University of Yamanashi |
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Principal Investigator |
ISHIKAWA Itsuo University of Yamanashi, Department of Research Interdisciplinary graduate School of medicine and Engineering, professor, 大学院・医学工学総合研究部, 教授 (00020446)
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| Project Period (FY) |
2004 – 2005
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| Keywords | public address system / moderate hearing loss / compansion / digital signal processing / improved listening / 実時間処理 |
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| Research Abstract |
The aim of the present study was to develop a public address system for assisting listening persons with moderate hearing loss. The procedure involved splitting the input signal into a number of smaller frequency bands using band-pass filters, followed by appropriate compansion of the output from each filter. The instantaneous value of the voltage signal, v, is processed successively by the equation w=sgn(v)c(|v|/v_c)^n, where w is the instantaneous output, sgn(v) is the sign function, and c and n are constants for the linear amplification rate and compansion rate, respectively. This process gives rise to odd harmonics which must be removed using a low-pass filter after which the output signal for the public address can then be obtained by adding these low-pass filter outputs.
The following results have been clarified by the present research :
1. Although the method requires considerable data processing, real time processing is possible with a commercially available digital signal processing circuit.
2. Since the amplification factor for a soft sound is markedly larger than for a loud sound, listening by impaired persons can be improved and the pain associated with loudness in persons with normal hearing can be suppressed.
3. The performance of the present method is superior to the output-limiting compression method employed by a product currently on the market.
The initial aims of developing a public address system for assisting moderately-impaired persons to listen to public address announcements were therefore satisfied
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