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.

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

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.

Acoustic Emission Minimization in a Wind Turbine Using Trip-Wires and Owl-Wing-Serrations

2015 ◽  
Author(s):  
Jafar Madadnia ◽  
Muhammad Fauzan Nurdin
Keyword(s):  
Wind Turbine ◽  
Acoustic Noise ◽  
Noise Cancellation ◽  
Speed Ratio ◽  
Combined Effects ◽  
Double Row ◽  
Single Row ◽  
Centre Frequency ◽  
Active Noise Cancellation ◽  
Active Noise

Acoustic noises emitted from wind turbine blades should be reduced to an acceptable level for the uptake of wind energy in buildings and in the urban environment. This paper reports on effectiveness of, Owl-wing-serrations (OWS), two-dimensional trip-wires, and Active-noise-cancellation (ANC) in minimization of aerodynamic noises in a micro model turbine. The OWS and trip wires were attached to the blade leading edges and trailing edges in the wind turbine. The model was operated in the fan mode as a single row. Combined effects of OWS and ANC were also tested in a counter rotating double-row Fan. Air velocity (m/s), shaft-revolution (rpm); electric-power (W), amplitude of acoustic noise (dB) and its Centre frequency (CF in Hz) were measured at a reference location, for a number of spacing. Experimental results were plotted in the forms of dB vs. Tip Speed Ratio (TSR), dB vs. CF, and Efficiency or Coefficients of Performance COP vs. TSR. It was noticed that • In the single row operations, 3mm trip wires and OWS attached to blades have influenced on the emitted aerodynamic noises. OWS reduced dB and increased Cf more than the trip-wires. For example, at a fixed TSR, amplitude of noise (dB) decreased with trip wires or OWS with the lowest dB occurring with the OWS alone. At a fixed dB, Centre frequency (Cf) increased with the highest frequency Cf occurring with OWS alone. Minor changes in efficiency (COP) were noticed with the trip wires or Owl-wing serrations. It may suggest that larger eddies are converted into small turbulences with lower amplitudes and higher frequencies. • Active-noise-cancellation (ANC) in the double row operation affected acoustic noises as spacing/gap between the counter-rotating rows changed. At a fixed TSR, dB decreased in the double row operations in comparison with the single-row operations, the reduction in dB increased at higher TSR. At a fixed dB, Centre frequency (Cf) increased by 100% with the highest frequency Cf occurring at the spacing of 50mm. Efficiency or COP decreased by 50% when ANC was implemented with a minor change due to spacing between rows. • Combined effects of OWS and ANC were moderate comparing to ANC alone, reducing both dB and COP by around 35% while doubling Cf as compared to the single raw fan conditions. The minimum dB and maximum Cf occurred at the gap/spacing of 50mm. No significant change was noticed at COP with combined OWS and ANC.

scholarly journals Implementation of Active Noise Cancellation for Small Confined Spaces

2020 ◽  
Vol 8 (6) ◽  
pp. 5575-5579
Keyword(s):  
Feedforward Control ◽  
Low Cost ◽  
Active Noise Control ◽  
Noise Pollution ◽  
Noise Cancellation ◽  
Noise Signal ◽  
Low Frequencies ◽  
Active Noise Cancellation ◽  
Active Noise ◽  
Noise Cancelling

Noise cancellation has slowly become a necessity instead of luxury. This is due to the increasing levels of noise pollution in today’s society. Exposure to prolonged and excessive noise has resulted in serious health problems ranging from stress, poor concentration and fatigue from lack of sleep, to more serious issues such as cardiovascular disease, cognitive impairment, tinnitus and hearing loss. Such noise pollution levels are also harmful to fetuses as low frequencies are not attenuated in the same way as high frequencies are attenuated by the mother’s womb. Recent techniques such as noise cancelling headphones, earbuds are being implemented that provide noise cancellation limited to a single person and not to a small room as a whole. Thus our paper proposes a duct system, which will be using the concept of active noise cancellation with the application of digital adoptive feedforward control, where an anti-noise signal is generated, having same amplitude as that of the noise signal but of reverse phase which when added together will cancel each other out. The adaptive filter is controlled by a microphone located in the duct to sense the noise reduction and adjust the entire system for optimum operation. The noise cancelling headphones that are being in use nowadays also operate on the same principle that is being implemented by our proposed system. But due to complex designs in the circuits such devices usually end up being too costly. So our system aims at providing a low cost solution. The system is mainly aimed at lower range of frequencies up to 1 KHz. Active noise control is being preferred as passive silencers are bulky and the attenuations achieved for low frequencies are relatively small.

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.

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