Investigation of aircrew noise exposure levels and hearing protection solutions in helicopter cabin

2016 ◽  
Vol 28 (8) ◽  
pp. 1050-1058
Author(s):  
Yong Chen ◽  
Sebastian Ghinet ◽  
Andrew Price ◽  
Viresh Wickramasinghe ◽  
Anant Grewal
Keyword(s):  
Air Force ◽  
Noise Exposure ◽  
Low Frequency ◽  
Noise Cancellation ◽  
Frequency Noise ◽  
Noise Attenuation ◽  
Active Noise Cancellation ◽  
Cabin Noise ◽  
Active Noise ◽  
Royal Canadian Air Force

High noise levels in the helicopter cabin adversely affect aircrew communication and reduce comfort in the short-term and may lead to hearing loss in the long-term if flight helmets cannot provide sufficient protection to the aircrew. A cabin noise exposure survey has been performed on a Royal Canadian Air Force CH-147F Chinook heavy lift helicopter to evaluate the noise environment and noise protection performance of the flight helmet. Investigation results showed that the low-frequency noise attenuation provided by the Royal Canadian Air Force flight helmet was marginal in high-speed flight conditions that generate loud cabin noise. Therefore, in-canal earphone integrated with active noise cancellation capability was investigated to provide enhanced noise protection and improve clarity in voice communication. Simulation and proof-of-concept test results verified that active noise cancellation in-canal earphones can serve as a feasible technical solution to provide enhanced noise attenuation to mitigate the low-frequency N/rev tonal noise generated by the aerodynamic pressure from the helicopter rotor blades.

EFFECTS OF AN ADAPTIVE-FEEDBACK ACTIVE NOISE CANCELLATION HEADSET ON WIDEBAND NOISE AND SPEECH INTELLIGIBILITY IN MANDARIN

2008 ◽  
Vol 20 (02) ◽  
pp. 123-131
Author(s):  
Jiun-Hung Lin ◽  
Shih-Tsang Tang ◽  
Wei-Ru Han ◽  
Chih-Yuan Chuang ◽  
Ping-Ting Liu ◽  
...  
Keyword(s):  
Speech Intelligibility ◽  
Low Frequency ◽  
Processing System ◽  
Noise Cancellation ◽  
Frequency Noise ◽  
Low Frequency Noise ◽  
Signal Processing System ◽  
Adaptive Feedback ◽  
Active Noise Cancellation ◽  
Active Noise

Many industrial workers must wear hearing protectors in order to avoid hearing loss. Conventional passive methods, such as earmuffs, are ineffective against low-frequency noise, and so the present study developed a headset equipped with a digital signal processing system that implements adaptive-feedback active noise cancellation (FbAANC) to reduce the low-frequency noise. The proposed FbAANC headset system reduced the noise level by 40–60 dB at frequencies down to 63 Hz. We also evaluated the effects of the FbAANC headset on speech intelligibility on a disyllabic Mandarin word discrimination test (WDT) platform. For an SNR below–10 dB, the mean WDT score was 13%–32% higher with the FbAANC headset than without the headset in 30 subjects with normal hearing thresholds. These results suggest that the FbAANC headset would be useful for hearing protection in workplaces with high levels of wideband industrial noise.

scholarly journals Active noise cancellation of low frequency noise propagating in a duct

2012 ◽  
Vol 1 (1) ◽  
pp. 24
Author(s):  
Farhad Forouharmajd ◽  
Masoumeh Ahmadvand ◽  
Parvin Nassiri ◽  
Farshad Forouharmajd
Keyword(s):  
Low Frequency ◽  
Noise Cancellation ◽  
Frequency Noise ◽  
Low Frequency Noise ◽  
Active Noise Cancellation ◽  
Active Noise

scholarly journals Performance Evaluation of Low Cost Analog Feedback Active Noise Cancellation System

2019 ◽  
Vol 8 (3S) ◽  
pp. 142-145
Keyword(s):  
Digital Signal Processor ◽  
Acoustic Noise ◽  
Low Cost ◽  
Low Frequency ◽  
Digital Signal ◽  
Noise Cancellation ◽  
Frequency Noise ◽  
Active Noise Cancellation ◽  
Active Noise ◽  
The Cost

Acoustic noise can be reduced by active noise cancellation (ANC) and passive noise cancellation (PNC) algorithm. The PNC can effectively attenuate the noise with high frequency, but not the noise with low frequency. ANC is one of the promising solution to reduce the low frequency noise. Commercial ANC headphones often use the digital signal processor (DSP) to perform the noise cancellation algorithm to cancel the annoying acoustic noise, but the cost is relatively high. A low-cost ANC solution is urgently needed to reduce the acoustic noise. The relationship between the frequency, distance and degree of magnitude of the noise level are also evaluated in this paper.

Communications Headset Augmentation via Active Noise Cancellation: Attenuation and Speech Intelligibility Performance

1993 ◽  
Vol 37 (9) ◽  
pp. 554-558
Author(s):  
John G. Casall ◽  
Daniel W. Gower
Keyword(s):  
Speech Intelligibility ◽  
Noise Exposure ◽  
Low Frequency ◽  
Noise Cancellation ◽  
Distinct Advantage ◽  
Pink Noise ◽  
Sound Fields ◽  
Active Noise Cancellation ◽  
Electronic Circuitry ◽  
Active Noise

Active noise cancellation (ANC) techniques utilize electronic circuitry to provide a phase-inverted sound wave, or “anti-noise,” to physically cancel the energy in an offending noise. This technique, originally used for abatement of noise in sound fields, has recently been refined and adapted to headset communications systems to 1) improve the speech/noise (S/N) ratio at the ear, and 2) reduce the noise exposure threat to hearing. ANC poses several important human factors issues encompassing speech intelligibility performance, attenuation performance, reliability and maintainability, and appropriateness of application to specific noise problems, all of which are addressed briefly in this paper. Also discussed is an experiment using a Bose Aviation Headset in its ANC mode, a Bose Aviation Headset in its non-active mode, and a conventional (non-ANC) David Clark H10-76 Headset. The Bose ANC unit required a significantly higher S/N ratio in tank and pink noise environments than the two passive headset systems to maintain equal intelligibility at a 70% level, in part due to its stronger noise reduction and a higher required speech level. In regard to hearing protection performance, the ANC device exhibited a distinct advantage, resulting in lower projected OSHA daily noise doses than either passive headset, with the largest increment in protection occurring in the low frequency-biased tank noise.

Development of an Active Noise Cancellation Hearing Protector: How Can Passive Attenuation Be Retained?

2005 ◽  
Vol 36 (11) ◽  
pp. 9-17 ◽  
Author(s):  
Mika Oinonen ◽  
Harri Raittinen ◽  
Markku Kivikoski
Keyword(s):  
Low Frequency ◽  
Noise Cancellation ◽  
Noise Attenuation ◽  
Active Noise Cancellation ◽  
Analog Electronics ◽  
Active Noise ◽  
Measurement Results ◽  
Proper Design ◽  
Hearing Protector ◽  
Passive Hearing

The modest low-frequency attenuation of the conventional passive hearing protector can be improved electronically by active noise cancellation techniques. This paper presents the theory and some of the actual limitations of an active noise cancellation hearing protector. Three prototypes with similar types of controller, but with different mechanical construction were made and their performance was measured. The electronics of the system were implemented using analog electronics and feedback construction. The measurement results were compared with the results of an equivalent passive hearing protector with no internal electronics and with an intact earcup. The results show that the integration of the controller inside the earcups degrades the passive attenuation of the hearing protector at frequencies below 200 Hz. With proper design, an active noise cancellation hearing protector can still have 15 dB more noise attenuation at 100 - 200 Hz range than an equivalent passive hearing protector.

Semi-adaptive active noise cancellation headphones

2021 ◽  
Vol 263 (2) ◽  
pp. 4717-4723
Author(s):  
Song Li ◽  
Roman Schlieper ◽  
Jürgen Peissig
Keyword(s):  
Ambient Noise ◽  
Adaptive Filters ◽  
Sudden Change ◽  
Dynamic Environments ◽  
Noise Cancellation ◽  
Noise Attenuation ◽  
Estimation Errors ◽  
Active Noise Cancellation ◽  
Active Noise ◽  
Relative Weighting

Active noise cancellation (ANC) headphones are becoming increasingly important as they can effectively attenuate perceived ambient noise. Fixed filters are commonly applied in commercially available ANC headphones due to their robustness. However, they are not capable of adapting to changes that occur in dynamic environments, resulting in degraded ANC performance. In contrast, adaptive filters are able to update the ANC filters to compensate for noise in dynamic environments, but large estimation errors can occur due to a sudden change in direction/type of noise or secondary path. Some studies have suggested an ANC system by combining fixed and adaptive filters. Based on this mechanism, we propose a semi-adaptive ANC system in which the fixed and adaptive filters are weighted in real-time. Initially, the weighting for the fixed filter dominates the whole system to ensure the robustness of the ANC system. Then, the residual error provided by the adaptive filter is simulated and compared to the real measured one to determine the relative weighting between the fixed and adaptive filters. In this study, this approach is applied to a feedback ANC system. Simulation results show that our proposed approach achieves high noise attenuation performance while maintaining robustness with time-varying secondary paths.

Noise Attenuation Effects on Speech Recognition of Cochlear Implant Users Inside Helicopters

2021 ◽  
Vol 92 (11) ◽  
pp. 880-885
Author(s):  
Juliana Maria Araujo Caldeira ◽  
Maria Valéria ◽  
Schmidt Goffi-Gomez ◽  
Rui Imamura ◽  
Ricardo Ferreira Bento
Keyword(s):  
Speech Recognition ◽  
Cochlear Implant ◽  
Noise Cancellation ◽  
Civil Aviation ◽  
Noise Attenuation ◽  
Background Condition ◽  
Radio System ◽  
Speech Processor ◽  
Active Noise Cancellation ◽  
Active Noise

BACKGROUND: The speech recognition levels of cochlear implant (CI) users are still incompatible with ICAO hearing requirements for civil aviation pilots testing in the noisy background condition of the helicopter cockpit. In this study, we evaluated noise attenuation effects on speech recognition in the same background condition.METHODS: The study involved the evaluation of 12 Portuguese-speaking CI users with post-lingual deafness and with a pure tone average up to 35 dB HL between 500 and 2000 Hz and up to 50 dB at 3000 Hz on at least one of the ears, and of three normal hearing pilots (controls). We performed speech recognition tests using sentences, numbers, and disyllables for all participants through the VHF radio. The assessment took place inside a helicopter with engine on, using three setups: 1) with headset without the active noise cancellation; 2) activating the noise cancellation system of the headset itself; and 3) connecting the speech processor directly to the helicopter radio system.RESULTS: The headset active noise-cancellation improved only the recognition of sentences. The direct connection system compared to the headset without anti-noise attenuation significantly improved all the recognition tests. The median for numbers was 90%, but the best score for disyllables recognition was 56%.DISCUSSION: The noise attenuation resources proposed in this study improved the CI users speech recognition when exposed to the noisy helicopter cockpit. However, speech recognition of CI users still did not meet the standards of ICAO, which requires at least 80% for understanding disyllables in the speech in noise test.Caldeira JMA, Goffi-Gomez MVS, Imamura R, Bento RF. Noise attenuation effects on speech recognition of cochlear implant users inside helicopters. Aerosp Med Hum Perform. 2021; 92(11):880-885.

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