Active Noise Reduction Headsets Research Articles

A feedforward and feedback composite active noise reduction headset based on inverse filter frequency equalization and its DSP system implementation

The principle of active noise reduction headset is to reduce the original noise by generating inverted noise through the loudspeaker. The loudspeaker system will introduce spectrum distortion inevitably. This distortion will increase the complexity of the secondary channel model, which adversely affect identification of the primary channel in the real-time active noise reduction system. To improve the inherent frequency spectrum distortion of the speaker system, this paper proposes a new frequency equalization method based on inverse filtering. This method is applied to a feedforward and feedback compound active noise reduction earphone system, and a new active noise reduction headphone system is obtained. In order to improve the noise reduction effect, the pollution caused by the secondary sound source to the reference signal is compensated in the active noise reduction control scheme of this paper. Simulation and real-time noise reduction experiments based on DSP solution show that this new active noise reduction control system can achieve better noise reduction effects.

Attenuation performance of active noise reduction headsets using American National Standard s12.42 and the proposed U.S. Environmental Protection Agency Hearing Protector Labeling Regulation

The attenuation performance and noise reduction rating (NRR) of six commercially available active noise reduction (ANR) headsets was assessed using the proposed environmental protection agency (EPA) regulation. The passive attenuation results were collected using American National Standard Institute (ANSI) S12.6 method for measuring real-ear attenuation at threshold (REAT) of hearing protectors while the active attenuations results were collected using ANSI S12.42 methods for the measurement of insertion loss of hearing protection devices in continuous or impulsive noise using microphone-in-real-ear (MIRE) or acoustic test fixture procedures. ANSI/ASA S12.68 methods of estimating effective A-weighted sound pressure levels when hearing protectors are worn was used to compute noise reduction metrics including the noise reduction statistic A-weighted (NRSA) and the graphical noise reduction statistic (NRSG). The proposed NRR labels for the ANR headsets were computer per the guidance in the draft U.S. EPA regulation. The presentation will include the baseline passive, active, and total attenuation, the NRSA and the Graphical NRSG, and the proposed EPA labels for passive attenuation and total attenuation while in an active mode.

Impulse Noise: Theoretical Solutions to the Quandary of Cochlear Protection

Workers in industries with impact noise, as well as soldiers exposed to supersonic blasts from armament and explosive devices, appear to be more at risk for hearing loss than are their counterparts exposed to continuous noise. Alternative considerations for hearing protection are dictated because of a disproportionately increased biophysical response in comparison to continuous noise. Impulse noise is a significant and distinct problem that requires a new strategy for hearing protection. A review of current clinical and occupational literature suggests that impulse noise may be more damaging than continuous sound. Statistical measurements such as kurtosis hold promise for the quantitative prediction of hearing loss. As sound energy to the cell increases, the mechanism of cochlear damage shifts from biochemical injury to mechanical injury. Outer hair cells appear to be more sensitive than inner hair cells to impulse noise because of their energy requirements, which lead to increased production of reactive oxygen and nitrogen species and self-destruction by apoptosis. Hearing protective devices currently in use for impulse noise include hunters' hearing devices, active noise-reduction headsets, and various in-ear plugs, including nonlinear reacting inserts. Existing equipment is hampered by the materials used and by present-day electronic technology. Antioxidants administered before sound exposure show promise in mitigating hearing loss in industrial and combat situations. New materials with improved damping, reflective, and absorption characteristics are required. Hearing protective devices that allow passage of ambient sound while blocking harmful noise might improve the compliance and safety of those exposed. Sensing devices that instantaneously and selectively hyperpolarize outer hair cells are discussed as alternate protection.

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

Biomedical Engineering: Applications, Basis and CommunicationsVol. 20, No. 02, pp. 123-131 (2008) No AccessEFFECTS OF AN ADAPTIVE-FEEDBACK ACTIVE NOISE CANCELLATION HEADSET ON WIDEBAND NOISE AND SPEECH INTELLIGIBILITY IN MANDARINJiun-Hung Lin, Shih-Tsang Tang, Wei-Ru Han, Chih-Yuan Chuang, Ping-Ting Liu, and Shuenn-Tsong YoungJiun-Hung LinDepartment of Electronics Engineering, Kun Shan University, Taiwan, R.O.C.Corresponding author: Professor Jiun-Hung Lin, Department of Electronics Engineering, Kun Shan University, No. 949, Da Wan Rd., Yung-Kang City, Tainan Hsien, Taiwan. Search for more papers by this author , Shih-Tsang TangDepartment of Biomedical Engineering, Yuanpei University, Taiwan, R.O.C. Search for more papers by this author , Wei-Ru HanInstitute of Biomedical Engineering, National Yang-Ming University Taiwan, R.O.C. Search for more papers by this author , Chih-Yuan ChuangInstitute of Biomedical Engineering, National Yang-Ming University Taiwan, R.O.C. Search for more papers by this author , Ping-Ting LiuInstitute of Biomedical Engineering, National Yang-Ming University Taiwan, R.O.C. Search for more papers by this author , and Shuenn-Tsong YoungInstitute of Biomedical Engineering, National Yang-Ming University Taiwan, R.O.C. Search for more papers by this author https://doi.org/10.4015/S1016237208000672Cited by:0 PreviousNext AboutSectionsPDF/EPUB ToolsAdd to favoritesDownload CitationsTrack CitationsRecommend to Library ShareShare onFacebookTwitterLinked InRedditEmail AbstractMany 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.Keywords:Noise cancellationWord discrimination testDSPIndustrial noise References S. M. Kuo and D. R. Morgan, Proc. IEEE 87(6), 943 (1999), DOI: 10.1109/5.763310. Crossref, ISI, Google ScholarS. J. Elliott and P. A. Nelson, IEEE Signal Process. Mag. 10(4), 12 (1993), DOI: 10.1109/79.248551. Crossref, ISI, Google ScholarH. Sano, S. Adachi and H. 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Comput. 43(5), 648 (2005), DOI: 10.1007/BF02351039. Crossref, ISI, Google Scholar Remember to check out the Most Cited Articles! Notable Biomedical TitlesAuthors from Harvard, Rutgers University, University College London and more! FiguresReferencesRelatedDetails Recommended Vol. 20, No. 02 Metrics History Accepted 3 February 2008 KeywordsNoise cancellationWord discrimination testDSPIndustrial noisePDF download

Comparison of passive versus active noise reduction headsets in light aircraft cockpit noise: Communications intelligibility and workload

Under instrument flight rules (IFR) conditions in Cessna 172R (95 dBA) cockpit noise, eight IFR-licensed pilots flew four 3.5-h nonstop flights in an FAA-certified, single-engine flight simulator, while wearing one of four communications headsets in each flight. All flights imposed an equivalently high level of air traffic control communications, at three Speech Transmission Index (STI) values: 0.30, 0.50, and 0.70. Perceptual and psychomotor workload were also controlled. In addition to a battery of flight-related metrics (some reported elsewhere), an objective, flight-embedded measure of communications intelligibility was obtained—the number of readbacks required of the pilot to attain 100% intelligibility on each command. An ANOVA revealed that as a group, the ANR headsets (Sennheiser HMEC300, Bose Aviation X, LightSPEED Thirty3G) required significantly fewer readbacks (averaging 1.2–1.3) than did the passive David Clark H-10-13.4 (averaging 1.5). Flight control performance, as reflected by deviations in assigned magnetic heading, altitude, and airspeed, was highest during flights with the Bose headset. Pilots’ workload estimates were measured using the modified Cooper-Harper scale, with 1 representing lowest workload and 9 representing highest. The three ANR headsets were associated with average workload ratings of 3.4–3.5, while the passive headset yielded a higher average workload of 4.4.

Anr vs. Passive Communications Headsets: Investigation of Speech Intelligibility, Pilot Workload, and Flight Performance in an Aircraft Simulator

Cockpits of propeller-driven aircraft are often environments of high amplitude, low frequency-dominant engine noise. This noise can interfere with radio communications. Previous authors have examined the effect of active noise reduction (ANR) headsets on speech intelligibility in noise in the absence of the attentional demand from simultaneously-performed complex tasks such as flying an airplane. This experiment investigated the combined effects of various headsets (passive and ANR) on speech intelligibility, mental workload and flight performance in an aircraft simulator. Instrument-rated pilots were tasked with completing four 3.5-hour cross-country flight simulations, one for each of 4 headsets. Results indicated that ANR headsets (as a group) generally improved speech intelligibility and decreased mental workload over a passive headset; however, flight performance results showed a more complex relationship. One conclusion is that a well-designed ANR headset has measurable benefits as a tool to potentially improve pilot performance by fostering safer operations within aviation systems.

Active noise reduction hearing protectors; 50 years of development

This paper will review the technology development of active noise reduction (ANR) hearing protectors. Such devices have been in development for close to 50 years. Early studies by Meeker on feedback implementation of ANR identified many of the issues and performance criteria that are still relevant today. These issues include compensation, minimum phase filter design, and out-of-band control stability. Numerous patents and publications since the early developments focused on means to address the issues discussed by Meeker, and, to introduce alternative implementations of ANR hearing protectors or headsets. Such alternatives include feed-forward designs, as well as open-back and closed-back designs (open-back designs rely solely upon active control for noise protection; closed-back designs include passive attenuation from an ear muff). Development has also proceeded on designs which include communication elements; here, the active control system must attenuate the noise, but not the communication. Fifty years on, ANR hearing protectors represent the most successful commercial application of active noise control technology.

Effects of Spatial Intercoms and Active Noise Reduction Headsets on Speech Intelligibility in an AWACS Environment

An experiment was conducted aboard an E-3 Airborne Warning and Control System aircraft to assess the ability of spatial intercoms and active noise reduction (ANR) headsets to improve communications effectiveness for air battle managers. Eleven male participants completed four blocks of data collection using the Coordinate Response Measure under factorial combinations of spatialization, ANR, and target phrase location. Results indicate that the use of a spatial intercom led to greater intelligibility, and that ANR improved intelligibility only when used in combination with a spatial intercom. These results are discussed in terms of their applicability to current and future USAF application domains.

Insertion loss testing of active noise reduction headsets using acoustic fixture

Active Noise Reduction (ANR) technique has been available for hearing protectors and communication headsets for years. However, no standard testing method for ANR headsets has emerged. In this study, we measured insertion losses of four types of commercially available ANR headsets using an Acoustic Test Fixture (ATF) to examine the feasibility of using ATF for this kind of measurement. The measurement outlined required a minimum of instrumentation and was relatively simple to implement. The results show that this method should be especially useful for testing of prototypes and for quality control as well.

The effects of completely-in-the-canal hearing aids, active noise reduction headsets, and ambient noise on speech intelligibility

Many people with hearing loss need to communicate and work in high noise environments. Hearing aids and headsets are often worn to protect the ear from further damage and facilitate communication. The purpose of this study was to determine the effects of the active noise reduction (ANR) headsets and Completely-in-the-Canal (CIC) hearing aids on speech intelligibility in ambient noise. Six male listeners with noise-induced hearing loss were each fitted with two digital CIC hearing aids. The listeners wore the hearing aids successfully for one year. The speech stimuli were presented over the ANR headphones in quiet and in 95 dB and 105 dB SPL of ambient pink noise. The independent variables were the active noise reduction, hearing aids, and noise level. All MRT stimuli were presented at the most comfortable loudness level. The dependent variable was speech intelligibility as measured with the Modified Rhyme Test (MRT). A main effect was discovered for noise, however no effect was found for active noise reduction or hearing aids. Although no overall effect was found with ANR or hearing aids on speech intelligibility there were differences across phoneme identifications and initial and final consonants.

Space Shuttle Noise and Active Noise Reduction Effects on Speech Intelligibility

This study tested the effects of active noise reduction (ANR) technology upon speech intelligibility under conditions of simulated space shuttle mid-deck noise. Thirty-two participants (16 male, 16 female) were tested with and without ANR headsets in a repeated measures design. A pre-recording of eight presenter voices (4 male, 4 female) reciting test words from the Modified Rhyme Test (MRT) was played in the presence of space shuttle mid-deck noise for each condition. There were significant differences in speech intelligibility with the use of ANR headsets, and between speech presenters. The scores obtained with the use of the ANR headsets were lower (less intelligible) than scores gained without the headsets. Gender and order effects were not observed. It is concluded that the type of ANR headset tested in this study will not aid speech intelligibility in the shuttle mid-deck noise environment.

A comparison of ANR headset performance for loopshaping and H∞ control system design

Active noise reduction (ANR) has been widely accepted as a critical component in circumaural hearing protectors and communication headsets for many commercial and military applications. That is because ANR headsets provide the end-user with at-ear noise suppression that is more effective than passive configurations alone can offer. In the past few years, there have been significant advances in this technology area. These are largely related to attempts to transition from traditional analog control hardware to digital implementations. One benefit of digital controller design is the ease of constructing optimal and robust compensators. The traditional approach in designing feedback ANR headsets is usually ‘‘loopshaping,’’ which is a somewhat heuristic design method. The desire for further improvements in feedback ANR headset performance is leading engineers toward more analytical approaches for controller design, including the robust techniques of H∞. This presentation compares and contrasts loopshaping and optimal controller design for the single-input, single-output disturbance rejection problem. A controls engineer experienced in loopshaping design techniques and a controls engineer experienced in optimal controller design techniques compare results for an ANR headset design. Constraints are placed on bandwidth, actuator force, and system design. It is shown that the loopshaping design can perform as good as or better than the optimal control solution for the given constraints.

Active noise reduction for cellular and PCS handsets

The effectiveness of active noise reduction (ANR) technology in Prototype cellular and PCS handsets has been investigated by developing prototype terminals with both feedback and feedforward control approaches. In contrast to ANR headsets, which present a relatively stable and favorable earpiece (i.e., receiver-error-microphone) transfer function (TF) to the ANR control system, an even greater challenge is faced in applying ANR to cellular/PCS handsets where the corresponding TF varies with positioning of the earpiece about the ear. As a first step in the investigation, a practical cellular/PCS handset earpiece, suitable for ANR, but with reduced position variability in the earpiece TF, has been developed using a lumped parameter, equivalent circuit model of the earpiece–ear system. Experimental results are presented for the new earpiece design tested against different users’ ears and against several acoustic load impedances. As the next step in the investigation, both feedback and fixed feedforward ANR control algorithms were implemented on a low-latency programmable ASIC developed specifically for ANR applications. The ANR performance results are presented for both feedback and feedforward designs tested against a range of users and also as measured against a B&K 4195 ‘‘leaky’’ coupler.

Active noise reduction headset

An active noise reduction headset including a headband and at least one earcup secured thereto. A microphone is mounted within the earcup for detecting and transducing acoustic pressure within the earcup to a corresponding microphone electronic signal. An electronic signal processing unit is mounted within the earcup and coupled with the microphone for generating an anti-noise signal from the microphone electronic signal. A first speaker is mounted within the earcup for receiving and acoustically reproducing an electronic anti-noise signal from the electronic signal processing unit. A second speaker is mounted within the earcup for receiving and acoustically reproducing an electronic communication signal.

The Effect of Active Noise Reduction Technology on Noise Induced Pilot Fatigue and Associated Cognitive Performance Decrements

Fatigue in the general aviation cockpit is caused by a variety of factors including cockpit noise. Active Noise Reduction (ANR) headsets have been proposed as a method to decrease cockpit noise and thereby decrease fatigue and the cognitive performance decrements associated with fatigue. The present study contrasted the subjective fatigue and cognitive performance of Certified Flight Instructors (CFI) during a day of in-air flight instruction with ANR headsets versus conventional headsets. CFIs exhibited increased subjective fatigue and a pattern of more rapid but less accurate cognitive performance at the end of an instructional day. However, subjective fatigue and cognitive performance changes did not differ as a function of type of headset worn. The results suggest that subjective fatigue increases and cognitive performance changes occur during a day of flying but they provide no evidence that the use of ANR headsets modify these changes.

Measuring the performance of circumaural hearing protectors and communication head sets at low frequencies

An enclosure has been constructed to evaluate the performance of active noise reduction (ANR), circumaural head sets, and hearing protectors, at frequencies below 800 Hz. It consists of a massive (5‐kg), flat base plate against which one cup cushion is sealed by spring pressure. The sound pressure within the cup is recorded by a microphone flush‐mounted in the base plate. A 20‐cm‐diam aluminum tube, 20 cm in length, is attached by annular flanges to the base plate at one end and, at the other, to a 15‐cm‐diam loudspeaker, which drives the enclosed volume so formed. The excitation of cross modes within the tube is suppressed by a 2.0‐cm cylindrical annular layer of felt, in contact with the inner wall of the tube. The performance of the measuring system will be described and results reported for the attenuation of an analog ANR head set. [Work done in collaboration with the Defence and Civil Institute of Environmental Medicine.]

History and development of active noise reduction hearing protection

Ever since Lueg's 1936 patent, the application of active noise reduction technology to hearing protection has been a goal of numerous research groups. This paper will describe the various efforts to apply active noise reduction technology to earcups over the time span from 1936 through the present. Each of the various efforts will be described in terms of basic cancellation technique, hardware realization, and both laboratory and field performance when available. In addition, a working model of the current active noise reduction headset developed jointly by the Air Force and Bose Corporation, similar to the unit used on the around the world flight of the Voyager, will be presented.