1,720,973 research outputs found
Design and implementation of an active noise control headphone with directional hear-through capability
No full textThis article presents the design and implementation of an active noise control (ANC) headphone system with a directional hear-through capability and compares the performance of this system to that of a standard hear-through headphone system. The directional hear-through ANC headphones are a novel integration of microphone array beamforming and ANC technologies into a pair of headphones, which provide the consumer with additional functionality and new, digitally augmented ways to interact with their acoustic environment. As the microphone array is necessarily compact, superdirective beamforming is utilised to increase its low and mid frequency directional performance. In this unique integration of two current consumer technologies, first, the ANC subsystem attempts to maximise the attenuation and then the beamformer output is added to the control signal and reproduced by the headphones' loudspeakers, with the appropriate compensation to avoid self-cancellation. The experimental study demonstrates that the proposed spatially selective ANC headphones provide a hear-through capability in the look direction, whilst reducing ambient noise and enabling the wearer to experience reduced noise communication in a noisy environment. The proposed system thus offers the consumer the potential for an electronically enhanced acoustic experience, allowing a selective reduction in environmental noise whilst desired exterior noise remains audible.</p
A hybrid multi-reference subband control strategy for active noise control headphones
No full textMulti-reference feedforward Active Noise Control (ANC) has been shown to provide increased noise mitigation capability in ANC headphones compared to a single reference feedforward controllers, due to the availability of additional time advanced information. Recent studies have also shown that the integration of a single-reference feedforward controller and a feedback controller increases both the noise cancellation bandwidth and system stability, therefore, a corresponding hybrid version of the multi-reference control strategy has been developed and is presented in this paper. The hybrid multi-reference ANC (HMRANC) system is comprised of a multi-reference feedforward control unit acting in conjunction with a feedback ANC system. In addition, to overcome the high computational demand of the hybrid structure, a delayless subband version of the HMRANC system is also presented in this paper. The proposed HMRANC and delayless subband HMRANC headphone systems achieve an improvement of 5–10 dB over the previously proposed hybrid ANC headphone system for different acoustic field scenarios. Moreover, the delayless subband HMRANC headphone system is 40% less computationally demanding then HMRANC and 10% less demanding than HANC headphone systems
Modified phase-scheduled-command FxLMS algorithm for active sound profiling
Full text linkActive sound profiling, or active noise equalization strategies have been proposed to achieve spectral shaping of a primary disturbance signal. The control algorithms proposed to achieve such spectral shaping have either suffered from poor robustness to plant modelling uncertainties or required high levels of control effort. To improve the robustness of active sound profiling to uncertainties in the plant model, whilst avoiding increased control effort, a modified phase-scheduledcommand filtered-x least-mean-square (FxLMS) algorithm is proposed in this paper. The new algorithm provides improved stability, whilst requiring the minimum control effort. This improvement is achieved by replacing the plant model with an intelligent adaptive-hysteresis switching mechanism to allow the necessary estimation of the disturbance signal phase. The improved performance and robustness of the proposed algorithm is demonstrated through a series of simulations using measured acoustic responses
The application of a multi-reference control strategy to noise cancelling headphones
No full textActive noise cancelling (ANC) headphones have seen significant commercial success and a number of control strategies have been proposed, including feedforward, feedback and hybrid configurations, using both analogue and digital implementations. Irrespective of the configuration or implementation approach, the strategies proposed in the open-literature have focused on implementations where the control system for each ear of the headphones operates independently. In this paper, a multi-reference ANC strategy is proposed and investigated for noise cancelling headphones. As with standard feedforward ANC headphones, the system utilises a single error microphone and single reference microphone on each cup, however, in the proposed configuration the left and right reference microphones are used to achieve control at both the left and right ear cups. The performance of this controller design is compared to a standard single reference feedforward controller implementation under a variety of different sound field conditions. Although the proposed strategy requires an increased computational demand, it is shown that there is a significant control advantage for noise sources originating from the side of the user, whilst the performance for front and rear sources is maintained
Hybrid feedback active noise control headset based on binaural signal utilization
No full textA standard feedback active noise control (FBANC) headset utilizes the estimate of a primary disturbance at the left-ear (right-ear) error microphone to control noise only at the left (right) ear-cup, i.e., each ear’s controller works independently. In contrast to the FBANC headset, in this paper, a binaural hybrid feedback active noise control (HFBANC) headset is designed that uses the estimate of the primary disturbances at both the left and right-ear error microphones to achieve improved noise control at both the left and right ear-cups. To further improve noise cancellation performance, the nearest Kronecker product decomposition technique is incorporated into the algorithm. The performance of the proposed HFBANC headset is compared to the standard FBANC headset under a variety of different sound field conditions. Experimental results show an improvement of 3–5 dB in the noise cancellation using the proposed algorithms, where the benefits are more prominent for noise sources originating from the side of the user (left and right)
Design of hybrid nonlinear spline adaptive filters for active noise control
No full textThis paper introduces a class of hybrid nonlinear spline filters, which are designed as a cascade of an adaptive spline activation function and a single layer adaptive nonlinear network. The adaptive nonlinear networks employed in this work are the functional link network (FLN) and the even mirror Fourier nonlinear (EMFN) network. Suitable update rules, which not only update the adaptive weights of the nonlinear networks, but also introduce adaptability in the developed spline function. The proposed nonlinear filters have been successfully applied to nonlinear system identification as well as nonlinear active noise control. The new filters have been shown to outperform the other popular nonlinear filters compared in the study
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
- …
