Noise is everywhere and in most applications that are related to audio and speech, such as human-machine interfaces, hands-free communications, voice over IP (VoIP), hearing aids, ...teleconferencing/telepresence/telecollaboration systems, and so many others, the signal of interest (usually speech) that is picked up by a microphone is generally contaminated by noise. As a result, the microphone signal has to be cleaned up with digital signal processing tools before it is stored, analyzed, transmitted, or played out. This cleaning process is often called noise reduction and this topic has attracted a considerable amount of research and engineering attention for several decades. One of the objectives of this book is to present in a common framework an overview of the state of the art of noise reduction algorithms in the single-channel (one microphone) case. The focus is on the most useful approaches, i.e., filtering techniques (in different domains) and spectral enhancement methods. The other objective of Noise Reduction in Speech Processing is to derive all these well-known techniques in a rigorous way and prove many fundamental and intuitive results often taken for granted. This book is especially written for graduate students and research engineers who work on noise reduction for speech and audio applications and want to understand the subtle mechanisms behind each approach. Many new and interesting concepts are presented in this text that we hope the readers will find useful and inspiring.
► Active noise control system which is robust against disturbances. ► Based on a functional link artificial neural network. ► Does not require selection of thresholds. ► Simulation study reveals ...enhanced performance.
The performance of a nonlinear active noise control (ANC) system based on the recently developed filtered-s least mean square (FsLMS) algorithm deteriorates when strong disturbances in the ANC system are acquired by the microphones. To surmount this shortcoming, a novel robust FsLMS (RFsLMS) algorithm is proposed for a functional link artificial neural network (FLANN) based ANC system. The new ANC system is least sensitive to such disturbances and does not call for any prior information on the noise characteristics. The results obtained from simulation study establish the effectiveness of this new ANC scheme.
Bu çalışmada sincap kafesli asenkron motorların rotor çubuklarındaki kırıkların akustik ölçümler ile tespiti incelenmiştir. Bu tip motorlar sanayide çok yaygın olarak kullanılmaktadır. Motorların ...rotor çubuklarındaki kırıklar motor performansını düşürür. Bu da üretimi aksatır ve maddi kayba neden olmaktadır. Çalışan motorda yapılacak akustik ölçümlerle bu tip arızaların önceden tespiti yapılabilir. Bu plansız duruşların ortadan kaldırılmasını sağlar. Akustik ölçümlerde elde edilen ses dosyaları için hazırlanan test devresinde ac sürücü, motor frenleme devresi ve kondenser mikrofon kullanılmıştır. MATLAB yazılımı ile zaman domenindeki değişimin Hızlı Furier Dönüşümü (FFT) yapılarak frekans domenindeki değişimler elde edilmiştir. Sağlam ve rotor çubuğu kırık olan motora ait farklı hız ve tork değerlerinde çalışması sırasında ölçülen ses dosyalarındaki FFT farkları tespit edilerek yorumlanmıştır.
Additive noise is ubiquitous in acoustics environments and can affect the intelligibility and quality of speech signals. Therefore, a so-called noise reduction algorithm is required to mitigate the ...effect of the noise that is picked up by the microphones. This work proposes a general framework in the time domain for the single and multiple microphone cases, from which it is very convenient to derive, study, and analyze all kind of optimal noise reduction filters. Not only that all known algorithms can be deduced from this approach, shedding more light on how they function, but new ones can be discovered as well.
Zusammenfassung
Private Drohnen im Aufwärtstrend.
Es werden immer mehr private Flugdrohnen verkauft und genutzt. Sie fotografieren und filmen uns von oben, selbst wenn wir in unserem Garten liegen ...oder in unserem Haus sind, am Fenster vorbeigehend oder stehend. Aus der Sicht der Informationsethik, die im vorliegenden Beitrag eingenommen wird, gibt es viele Risiken beim Einsatz, aber auch einige Chancen, und zwar sowohl für die Besitzer als auch für die Betroffenen. Zu den herausgearbeiteten Risiken zählt die Gefährdung der informationellen und persönlichen Autonomie, zu den Chancen die Erweiterung menschlicher Möglichkeiten mithilfe der Informationstechnologie.
The book reflects the state of the art in important areas of speech and audio signal processing. It presents topics which are missed so far and most recent findings in the field. Leading ...international experts report on their field of work and their new results. Considerable amount of space is covered by multi-microphone systems, specific approaches for noise reduction, and evaluations of speech signals and speech processing systems. Multi-microphone systems include automatic calibration of microphones, localisation of sound sources, and source separation procedures. Also covered are recent approaches to the problem of adaptive echo and noise suppression. A novel solution allows the design of filter banks exhibiting bands spaced according to the Bark scale und especially short delay times. Furthermore, a method for engine noise reduction and proposals for improving the signal/noise ratio based on partial signal reconstruction or using a noise reference are reported. A number of contributions deal with speech quality. Besides basic considerations for quality evaluation specific methods for bandwidth extension of telephone speech are described. Procedures to reduce the reverberation of audio signals can help to increase speech intelligibility and speech recognition rates. In addition, solutions for specific applications in speech and audio signal processing are reported including, e.g., the enhancement of audio signal reproduction in automobiles and the automatic evaluation of hands-free systems and hearing aids.
After the sound reproduction industry had claimed “perfect high fidelity” for sound recordings already at the beginning of the twentieth century, composers and sound artists challenged this ...perfection by tweaking microphones and loudspeakers to make them act as a musical instrument instead of a mere sound reproduction device. This book explores the instrumental use of microphones and loudspeakers in music beginning in the 1950s. The popular noise musician Merzbow, over-minimalist classic Alvin Lucier, cult instrument inventor Hugh Davies, and contemporary visual artist Lynn Pook made audible what was supposed to remain silent.
This work addresses this problem in the short-time Fourier transform (STFT) domain. We divide the general problem into five basic categories depending on the number of microphones being used and ...whether the interframe or interband correlation is considered. The first category deals with the single-channel problem where STFT coefficients at different frames and frequency bands are assumed to be independent. In this case, the noise reduction filter in each frequency band is basically a real gain. Since a gain does not improve the signal-to-noise ratio (SNR) for any given subband and frame, the noise reduction is basically achieved by liftering the subbands and frames that are less noisy while weighing down on those that are more noisy. The second category also concerns the single-channel problem. The difference is that now the interframe correlation is taken into account and a filter is applied in each subband instead of just a gain. The advantage of using the interframe correlation is that we can improve not only the long-time fullband SNR, but the frame-wise subband SNR as well. The third and fourth classes discuss the problem of multichannel noise reduction in the STFT domain with and without interframe correlation, respectively. In the last category, we consider the interband correlation in the design of the noise reduction filters. We illustrate the basic principle for the single-channel case as an example, while this concept can be generalized to other scenarios. In all categories, we propose different optimization cost functions from which we derive the optimal filters and we also define the performance measures that help analyzing them.
This paper presents a mechanical positioning system for a measuring microphone designed for acoustic studies in anechoic and reverberation chambers at the Department of Mechanics and Vibroacoustics, ...AGH. The results are discussed in the context of mechanical positioning and its impact on the outcome of the execution of individual measurement procedures. Moreover, areas for research were identified and solution concepts shown for further development of the automation of acoustic measurements in different research rooms in order to reduce the human involvement in them.
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