In this paper we consider a physical model in which a buffer receives messages from a finite number of statistically independent and identical information sources that asynchronously alternate between exponentially distributed periods in the ‘on’ and ‘off’ states. While on, a source transmits at a uniform rate. The buffer depletes through an output channel with a given maximum rate of transmission. This model is useful for a data‐handling switch in a computer network. The equilibrium buffer distribution is described by a set of differential equations, which are analyzed herein. The mathematical results render trivial the computation of the distribution and its moments and thus also the waiting time moments. The main result explicitly gives all the system's eigenvalues. While the insertion of boundary conditions requires the solution of a matrix equation, even this step is eliminated since the matrix inverse is given in closed form. Finally, the simple expression given here for the asymptotic behavior of buffer content is insightful, for purposes of design, and numerically useful. Numerical results for a broad range of system parameters are presented graphically.

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Teleconferencing systems employ acoustic echo cancelers to reduce echoes that result from coupling between the loudspeaker and microphone. To enhance the sound realism, twochannel audio is necessary. However, in this case (stereophonic sound) the acoustic echo cancellation problem is more difficult to solve because of the necessity to uniquely identify two acoustic paths. In this paper, we explain these problems in detail and give an interesting solution which is much better than previously known solutions. The basic idea is to introduce a small nonlinearity into each channel that has the effect of reducing the interchannel coherence while not being noticeable for speech due to self masking.

High quality speech at low bit rates (e.g., 2400 bits/s) is one of the important objectives of current speech research. As part of long range activity on this problem, we have developed an efficient computer program that will serve as a tool for investigating whether articulatory speech synthesis may achieve this low bit rate. At a sampling frequency of 8 kHz, the most comprehensive version of the program, including nasality and frication, runs at about twice real time on a Cray-1 computer.