双通路立体声的三扬声器虚拟重发的实验研究

对现有的、将双通路立体声信号转换为前方三扬声器重发信号的虚拟声信号处理方法进行了改进，加入了音色均衡的信号处理。同时对该方法进行了主观和客观实验验证，结果表明，经虚拟声信号处理，三扬声器重发不但可得到和普通立体声重发一样的声像效果，而且可提高声像的稳定性，扩大听音区域。     

Quadraphony, Spatial High Fidelity, And Compatibility

The premise of this paper is that quadraphony is essential to true high fidelity, and that a most important criterion of merit of a quadraphonic system, in addition to its directional efficacy, is compatibility with the existing monophonic and stereophonic players and broadcast transmission/reception apparatus. It is argued that, given the usual dimensional limitations of electromagnetic spectrum, or the area of recording medium, or cost, matrix quadraphony is the preferred engineering solution and that the CBS SQ?matrix is the optimal matrix for this purpose. The unique advantages of the SQ matrix are phase integrity and total separation of front channels which transmit unaltered the concert stage sounds, and its in-quadrature coding of back channels which allows them to be "folded" optimally in the stereo mode and to be transmitted at full level in the monophonic mode, a combination not found in other matrix systems. Alternative systems are discussed and are found wanting because of relatively poor front-channel separation or phase-shifted center-front signal or excessive loss of the back-corner signals in monophonic reproduction, or all three deficiencies combined.     

An Amplitude Modulated Stereo System

An amplitude modulated stereophonic system, which is compatible with conventional monophonic AM systems, is presented in this paper. First, conditions on the envelope and phase function for the transmitted signal are derived. Then, a compatible quadrature AM(compatible QUAM) system is proposed for the transmission and reception of stereophonic program material. Some results of testing the proposed system are included.     

Three-Channel FM Stereo Multiplex System for Compatible Broadcasting

A system for transmitting and receiving three independent stereophonic channels by FM multiplex is described. This system has the advantage of being compatible with monophonic and two-channel stereophonic FM receivers without any significant loss in their output signal-to-noise ratios (less than 1 dB) and without having to utilize any part of the SCA band. Compatibility of the three-channel stereophonic receiver with a one-or two-channel broadcast is achieved by the use of an additional pilot signal that does not cause any increase in the instantaneous frequency deviation of the FM carrier. The additional noise in the output of the three-channel receiver appears to be less than 6 dB above the noise that is now present in two-channel receivers.     

Separation of several speakers recorded by two microphones (cocktail-party processing)

A signal processing method for enhancing the directional separation of an ordinary (dummy-head) stereophonic speech recording is described that, after initial adaptation to a certain direction, simulates the human ability to concentrate on speech coming from this direction and to suppress disturbing speakers from other directions. The method is derived from the principle of Adaptive Noise Cancelling; an FFT/Overlap-Add realization of the adaptive filter is chosen and short-time power estimates are used for its determination. In tests with up to four speakers, clear improvements of SNR and intelligibility of the desired speaker were obtained.     

一个基于盲信号分离的多路回波消除结构

多路回波消除问题的本质难点是由于多路输入信号之间的强相关性而导致的自适应滤波器解不唯一的问题.目前许多文献都是试图通过对输入信号预处理来解决这个问题,这些方法都对原输入信号作了变化,从而影响了通话质量.本文提出了一个简化的盲信号分离模型的立体声回波消除结构,在这个结构中,立体声回波消除问题被转化为两个单路的回波消除问题,从而避免了自适应滤波器解不唯一的问题.仿真结果证明了新结构的有效性.     

试论FM立体声广播发射机中锁相调频环路参数对立体声分离度的影响

本文分析了FM立体声广播发射机中锁相调频环路参数与立体声分离度的关系,给出了环路参数的设计原则。     

Transmission system with cascade phase modulation by dividing the baseband spectrum into subbands

In the proposed system, the baseband spectrum is divided into several subbands; each subband phase-modulates the carrier, by means of modulators in cascade, in a multiplication chain. This system allows the use of indirect frequency modulation for signals such as the stereophonic signal, the multiplex-telephone signal and the video-frequency signal.     

On joint coding for watermarking and encryption

In continuation of earlier work, where the problem of joint information embedding and lossless compression (of the composite signal) was studied in the absence and in the presence of attacks, here we consider the additional ingredient of protecting the secrecy of the watermark against an unauthorized party, which has no access to a secret key shared by the legitimate parties. In other words, we study the problem of joint coding for three objectives: information embedding, compression, and encryption. Our main result is a coding theorem that provides a single-letter characterization of the best achievable tradeoffs among the following parameters: the distortion between the composite signal and the covertext, the distortion in reconstructing the watermark by the legitimate receiver, the compressibility of the composite signal (with and without the key), and the equivocation of the watermark, as well as its reconstructed version, given the composite signal. In the attack-free case, if the key is independent of the covertext, this coding theorem gives rise to a threefold separation principle that tells that asymptotically, for long block codes, no optimality is lost by first applying a rate-distortion code to the watermark source, then encrypting the compressed codeword, and finally, embedding it into the covertext using a previously proposed embedding scheme. In the more general case, however, this separation principle is no longer valid, as the key plays an additional role of side information used by the embedding unit     

立体声耳机重发中头中定位效应的消除

探讨双通路立体声耳机重发中头中定位效应的消除。实验结果表明,如果仅用人头传输函数（ＨＲＴＦ）对声音信号进行处理,能产生一定的声像方向感,但还不能很好地消除头中定位效应,而通过加混响信号使声像有深度感,可在一定程度上起到改善的作用。     

一种基于逼近线性空间的盲信号分离方法

文章结合目标函数,给出了一种非线性混叠信号盲分离算法,含噪混合信号之间的关系构造了动态的目标函数状态一空间。该函数的特点是多变量,过程和观测噪声不限于高斯分布,是解决该问题的有效方法,从而把非线性混叠信号盲分离问题转化为参数空间的线性混叠信号盲分离问题。在目标函数空间中,也可应用多次分离对信号进行分离。该算法收敛精度较高,稳定性好。     

连续运动立体声像的心理声学实验

对双通道立体声和５通路３／２环绕声系统的运动声像进行了研究,指出了连续运动的立体声像中通过产生跳跃运动的声像而近似得到,用心理声学的实验方法探讨了运动声像在听觉上的连续性与声像的跳跃角度,运动速度,信号类型等的关系,实验还证明了采用现有的信号馈给法,在５通路３／２系统的一些路径（如侧向）是难以产生连续运动的声像的。研究结果对运动声像的模拟具有实际意义,在录音和信号处理过程中可以作为参考。     

Problems of Mono/Stereo Compatibility in Broadcasting

A monaural signal of broadcast quality may not always be produced by the simple combination of stereophonic information. Loss of musical balance, distortion from poor disk tracking, and phase cancellation are among the problems encountered.     

The Relative Effects of Deemphasis and Noise Weighting Networks on Stereophonic and Monophonic Signal to Noise Measurements

In making signal to noise ratio measurements for monophonic and stereophonic FM signals, the types of noise weighting circuit and deemphasis circuit used have significant effects on the results. In this paper the relative values of noise power are calculated and presented for several common deemphasis and weighting circuits and various types of noise spectra. With these results it is possible to meaningfully compare results obtained from different measurements and to predict how results will scale from one measurement to another.     

厅堂扩声声像的探讨

介绍了双路扬声器重放的原始声场效果，对使用强度型立体声拾声、双路扬声器重放扩声系统的厅堂会使声像(声源的幻像)位置和真实声源位置产生偏差，甚至出现严重的分离现象进行了分析。     

A Stereophonic System for Amplitude-Modulated Broadcast Stations

An AM stereophonic system is described which is compatible with existing receivers and transmitters, does not increase interference, and allows stereophonic reception with two conventional AM sets as presently found in many homes, or inexpensive home receiving equipment specifically designed for AM stereo.     

基于互补对称滤波器的APCMA信号的盲分离算法

针对小站信号带宽大于主站信号的新非对称成对载波多址（Asymmetric Paired Carrier Multiple Access,APCMA）信号背景,在一种低复杂度的盲抵消结构基础上,提出基于互补对称滤波器的盲分离算法.该算法采用互补对称滤波器从时频域上将混合信号分解为同时含主站信号与小站信号,以及只含小站信号的两路分量信号,在保证采样率不变的情况下对含主站信号的信号分量做进一步的信号分离,通过两路分量信号的同步处理确保了分离之后的两路信号分量中小站信号的可加性和完整性.仿真结果表明,与原低复杂度算法相比,本文算法有效地提升了混合信号的分离性能.此外,本文提出的具有信息不变性的互补对称滤波器有较广泛的应用前景,可用于宽带多信号抵消、信道估计以及隐蔽传输下的扩频检测等问题中.     

Eigenvalue communication

The authors propose a communication method for a nonlinear and dispersive medium such as an optical fiber that is based on eigenvalues of associated equations for the wave amplitude. In optical communications, the communication distance measured by the carrier wavelength reaches the order of 10/sup 11/-10/sup 13/. As a result, dispersive and nonlinear effects, even if small, contribute significantly to the distortion of signal information contained in waveforms or in frequency spectra. Thus, it is desirable to use other parameters which remain unaltered. The eigenvalues of the associated equation for the nonlinear Schrodinger equation which describes the lightwave envelope in fibers constitute such parameters. Soliton-based communication corresponds to the case of one eigenvalue.<>     

3D环绕立体声技术的数字化

ＳＲＳ３Ｄ环绕立体声技术充分利用“耳廓效应”只需两只音箱,就能从任意音源中恢复出３Ｄ环绕立体声,故ＳＲＳ环绕声效处理器在市场上倍受迎。文中利用数字信号处理技术和心理声学方面研究的最新成果,基于计算机多媒体系统,以ＶｉｓｕａｌＣ＋＋为工具开发了一播放器软件。     

Performance Comparison between Beamforming and Spatial Multiplexing for the Downlink in Wireless Cellular Systems

We compare the performance between beamforming and spatial multiplexing showing in which downlink scenarios the higher performance of spatial multiplexing justify its complexity. We compute performance using readily measurable parameters such as angle spread (AS), antenna separation and signal to noise ratio (SKIR). Firstly, a semi-analytical approach relates these measurable parameters with parameters that theoretically characterize beamforming optimality such as the spatial correlation matrix first two eigenvalues and SNR. Secondly, the achieved spectral efficiency is given for beamforming and spatial multiplexing as a function of antenna separation, AS and SNR. Also, a "practical" region is given where beamforming achieves at least 90% of the spectral efficiency of spatial multiplexing.