title: Hybrid feedforward-feedback active noise reduction for hearing protection and communication.
abstract: 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.
authors.affiliation: Thayer School of Engineering, Dartmouth College, 8000 Cummings Hall, Hanover, New Hampshire 03755, USA.
authors.forename: Laura R
authors.initials: LR
authors.lastname: Ray
authors.forename: Jason A
authors.initials: JA
authors.lastname: Solbeck
authors.forename: Alexander D
authors.initials: AD
authors.lastname: Streeter
authors.forename: Robert D
authors.initials: RD
authors.lastname: Collier
mesh_terms: D000401:Aircraft; D000465:Algorithms; D004430:Ear Protective Devices; D004867:Equipment Design; D005246:Feedback / Q000502:physiology*; D006317:Hearing Loss, Noise-Induced / Q000517:prevention & control; D006801:Humans; D008348:Manikins; D008954:Models, Biological; D009622:Noise / Q000009:adverse effects / Q000517:prevention & control*; D009624:Noise, Transportation / Q000517:prevention & control