Cross-power Spectrum Phase Research Articles

Robust Talker Direction Estimation Based on Weighted CSP Analysis and Maximum Likelihood Estimation

This paper describes a new talker direction estimation method for front-end processing to capture distant-talking speech by using a microphone array. The proposed method consists of two algorithms: One is a TDOA (Time Delay Of Arrival) estimation algorithm based on a weighted CSP (Cross-power Spectrum Phase) analysis with an average speech spectrum and CSP coefficient subtraction. The other is a talker direction estimation algorithm based on ML (Maximum Likelihood) estimation in a time sequence of the estimated TDOAs. To evaluate the effectiveness of the proposed method, talker direction estimation experiments were carried out in an actual office room. The results confirmed that the talker direction estimation performance of the proposed method is superior to that of the conventional methods in both diffused- and directional-noise environments.

Digital watermarks for audio signal based on psychoacoustic masking model

AbstractThis paper describes one digital watermarking method for audio signals using the MPEG psychoacoustic model. It is important that a digital watermark be perceptually inaudible to the human auditory system. One watermark algorithm that takes this into account is the digital watermark algorithm using the MPEG psychoacoustic model proposed by Boney and colleagues. However, this method has several drawbacks such as it is susceptible to MPEG encoding and there is no synchronized detection measure. As a result, several improvements were made to increase the robustness of the digital watermark to MPEG encoding, and information from psychoacoustic tests was also used to introduce successive masking. These improvements enabled a watermark to be implemented that is even robust to MPEG encoding. To ensure robustness to D‐A/A‐D conversions or cropping attacks, a whitened cross‐correlation method (cross‐power spectrum phase) was used to implement synchronized detection. This enabled a watermark that is robust to D‐A/A‐D conversions to be implemented. This watermark was also shown to be robust to attacks such as noise addition, filtering, and downsampling. In addition, this paper shows the results of subjective evaluation experiments, which indicate that there is little quality deterioration due to watermarking. © 2003 Wiley Periodicals, Inc. Electron Comm Jpn Pt 3, 86(12): 65–75, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecjc.10143

An evaluation of talker localization based on direction of arrival estimation and statistical sound source identification

It is very important to capture distant-talking speech for a hands-free speech interface with high quality. A microphone array is an ideal candidate for this purpose. However, this approach requires localizing the target talker. Conventional talker localization algorithms in multiple sound source environments not only have difficulty localizing the multiple sound sources accurately, but also have difficulty localizing the target talker among known multiple sound source positions. To cope with these problems, we propose a new talker localization algorithm consisting of two algorithms. One is DOA (direction of arrival) estimation algorithm for multiple sound source localization based on CSP (cross-power spectrum phase) coefficient addition method. The other is statistical sound source identification algorithm based on GMM (Gaussian mixture model) for localizing the target talker position among localized multiple sound sources. In this paper, we particularly focus on the talker localization performance based on the combination of these two algorithms with a microphone array. We conducted evaluation experiments in real noisy reverberant environments. As a result, we confirmed that multiple sound signals can be identified accurately between ‘‘speech’’ or ‘‘non-speech’’ by the proposed algorithm. [Work supported by ATR, and MEXT of Japan.]

Use of the crosspower-spectrum phase in acoustic event location

The article reports on the use of crosspower-spectrum phase (CSP) analysis as an accurate time delay estimation (TDE) technique. It is used in a microphone array system for the location of acoustic events in noisy and reverberant environments. A corresponding coherence measure (CM) and its graphical representation are introduced to show the TDE accuracy. Using a two-microphone pair array, real experiments show less than a 10 cm average location error in a 6 m/spl times/6 m area.

Estimation of wavefront arrival delay for acoustical signals using the cross-power spectrum phase technique

In order to provide spatially selective sound capture in a teleconferencing environment, microphone array systems require accurate determination of the location of the desired source. Sound source location in turn relies on estimating time delay of arrival (TDOA) of a sound wavefront across a given microphone sensor pair. The cross-power spectrum phase (CPSP) method [M. Omologo and P. Svaizer, ICASSP 94] may be used for TDOA estimation. It is desirable to operate microphone array systems in untreated acoustical environments. Such an environment may produce multipath sound propagation and may contain moderate sources of interfering noise. The TDOA estimates computed using CPSP may become unreliable in such an environment. A strategy is presented to extract reliable TDOA information from the CPSP algorithm. The following measures are included: spectral weighting of the CPSP function based on knowledge of noise and sound source statistics, measuring the accuracy of the CPSP function by examining its shape, and evaluating the CPSP only when the captured signal has appropriate energy and spectral characteristics. This strategy enables less error-prone performance, and allows more effective utilization of computing resources in a constrained real-time system. Simulation and real-time results are presented to demonstrate system improvement.

A DSP implementation of source location using microphone arrays.

The design, implementation, and performance of a low-cost, real-time DSP system for source location is discussed. The system consists of an eight-element electret microphone array connected to a Signalogic DSP daughterboard hosted by a PC. The system determines the location of a speaker in the audience in an irregularly shaped auditorium. The auditorium presents a nonideal acoustical environment; some of the walls are acoustically treated but there still exist significant reverberation and a large amount of low-frequency noise from fans in the ceiling. The source location algorithm is implemented in a two-step process: The first step determines time delay of arrival (TDOA) for select microphone pairs. A modified version of the cross-power spectrum phase method [M. Omologo and P. Svaizer, Proceedings of IEEE ICASSP 1994 (IEEE, New York, 1994), pp. II273–II276] is used to compute TDOAs and is implemented on the DSP daughterboard. The second step uses the computed TDOAs in a least-mean-square gradient descent search algorithm implemented on the PC to compute a location estimate. [Work supported by a contract with Bell Communications Research.]

Analysis of in-core dynamics in pressurized water reactors with application to parameter monitoring

The behavior of the phase relationship between neutron flux and core-exit temperature fluctuations in a pressurized water reactor (PWR) is studied as a function of the moderator temperature coefficient of reactivity ( α c). PWR operational data indicates that the neutron noise and core-exit temperature noise cross power spectrum phase is linear in a certain frequency range, and approaches −180 deg at low frequencies. Extensive modeling studies applied to the LOFT reactor shows that this low frequency phase behavior changes when α c is positive, approaching zero deg at low frequencies. The analysis further showed that in the LOFT reactor, coolant flow rate fluctuation is the primary driving source causing neutron noise and core-exit temperature fluctuations. This conclusion was also confirmed by independent studies. The neutron noise-coolant temperature phase behavior may be used as a simple method of monitoring the moderator temperature coefficient of reactivity during different stages of a PWR fuel cycle.