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Oct 2006

Volume 120, Issue 4, pp. 1743-EL54

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Broadband noise reduction of piezoelectric smart panel featuring negative-capacitive-converter shunt circuit

Jaehwan Kim and Young-Chae Jung

J. Acoust. Soc. Am. Volume 120, Issue 4, pp. 2017-2025 (2006); (9 pages) | Cited 1 time

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A broadband noise reduction of a piezoelectric smart panel featuring a negative capacitance converter (NCC) shunt circuit is experimentally investigated. Piezoelectric shunt damping utilized on the panel structure is attractive for noise reduction especially at low resonance frequencies of the structure. To achieve a broadband noise reduction, however, a multimode shunt is necessary. The NCC circuit can be an ideal broadband shunt circuit by nullifying the capacitance of the piezoelectric patch with the circuit. Since the intrinsic capacitance of the patch is not constant with the frequency, the broadband shunt performance of the NCC can be deteriorated. Thus, we introduce the dual-patch NCC circuit on the smart panel. The proposed concept is explained and the tuning and implementation procedures are addressed. The noise reduction performance of the panel is tested in terms of transmission loss according to the standard transmitted noise measurement. The broadband damping performance of the smart panel featuring a dual-patch NCC shunt is compared with the panels featuring resonant shunt circuit and ordinary NCC shunt circuit in terms of acceleration and noise transmission loss. It is found that the dual-patch NCC shunt is more efficient than ordinary NCC and resonant shunt for achieving broadband noise reduction with smart panels.
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43.50.Gf Noise control at source: redesign, application of absorptive materials and reactive elements, mufflers, noise silencers, noise barriers, and attenuators, etc.
43.50.Ki Active noise control
43.55.Wk Damping of panels
43.55.Rg Sound transmission through walls and through ducts: theory and measurement

Hybrid feedforward-feedback active noise reduction for hearing protection and communication

Laura R. Ray, Jason A. Solbeck, Alexander D. Streeter, and Robert D. Collier

J. Acoust. Soc. Am. Volume 120, Issue 4, pp. 2026-2036 (2006); (11 pages)

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A hybrid active noise reduction (ANR) architecture is presented and validated for a circumaural earcup and a communication earplug. The hybrid system combines source-independent feedback ANR with a Lyapunov-tuned leaky LMS filter (LyLMS) improving gain stability margins over feedforward ANR alone. In flat plate testing, the earcup demonstrates an overall C-weighted total noise reduction of 40 dB and 30–32 dB, respectively, for 50–800 Hz sum-of-tones noise and for aircraft or helicopter cockpit noise, improving low frequency (<100 Hz) performance by up to 15 dB over either control component acting individually. For the earplug, a filtered-X implementation of the LyLMS accommodates its nonconstant cancellation path gain. A fast time-domain identification method provides a high-fidelity, computationally efficient, infinite impulse response cancellation path model, which is used for both the filtered-X implementation and communication feedthrough. Insertion loss measurements made with a manikin show overall C-weighted total noise reduction provided by the ANR earplug of 46–48 dB for sum-of-tones 80–2000 Hz and 40–41 dB from 63 to 3000 Hz for UH-60 helicopter noise, with negligible degradation in attenuation during speech communication. For both hearing protectors, a stability metric improves by a factor of 2 to several orders of magnitude through hybrid ANR.
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43.50.Hg Noise control at the ear
43.50.Ki Active noise control
43.72.Dv Speech-noise interaction

The relationship between railway noise and community annoyance in Korea

Changwoo Lim, Jaehwan Kim, Jiyoung Hong, and Soogab Lee

J. Acoust. Soc. Am. Volume 120, Issue 4, pp. 2037-2042 (2006); (6 pages) | Cited 4 times

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A study of community annoyance caused by exposures to railway noise was carried out in 18 areas along railway lines to accumulate social survey data and assess the relationship between railway noise levels and annoyance responses in Korea. Railway noise levels were measured with portable sound-level meters. Social surveys were administered to people living within 50 m of noise measurement sites. A questionnaire contained demographic factors, degree of noise annoyance, interference with daily activities, and health-related symptoms. The question relating to noise annoyance was answered on an 11-point numerical scale. The randomly selected respondents, who were aged between 18 to 70 years of age, completed the questionnaire independently. In total, 726 respondents participated in social surveys. Taking into consideration the urban structure and layout of the residential areas of Korea, Japan, and Europe, one can assume that the annoyance responses caused by the railway noise in this study will be similar to those found in Japan, which are considerably more severe than those found in European countries. This study showed that one of the most important factors contributing to the difference in the annoyance responses between Korea and Europe is the distance between railways and houses.
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43.50.Qp Effects of noise on man and society
43.50.Sr Community noise, noise zoning, by-laws, and legislation
43.50.Rq Environmental noise, measurement, analysis, statistical characteristics
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