The first three representatives of a new generation of multimedia self-study courses designed to meet the IEEE's standards for self-paced instruction are described. They are a basic and an advanced course in digital signal processing (DSP) and an introduction to digital speech processing. While drawing heavily on established textbook, each course is built around the Macintosh platform and is driven by HyperCard stacks which in turn interface with a special educational edition of the DSP Designer signal processing simulation package. Optional additional components include high-quality sound I/O, a real-time DSP board, and bulk data storage devices (CD-ROM, VCR, compact disk, laser disk). An electronic mail network connects learners with each other and with the course author.>

A perceptually motivated objective measure for evaluating speech quality is presented. The measure, computed from the original and coded versions of an utterance, exhibits statistically a monotonic relationship with the mean opinion score, a widely used criterion for speech coder assessment. For each 10-ms segment of an utterance, a weighted spectral vector is computed via 15 critical band filters for telephone bandwidth speech. The overall distortion, called Bark spectral distortion (BSD), is the average squared Euclidean distance between spectral vectors of the original and coded utterances. The BSD takes into account auditory frequency warping, critical band integration, amplitude sensitivity variations with frequency, and subjective loudness.>

A novel perceptually motivated objective measure for estimating the subjective quality of coded speech is presented. It takes into account auditory frequency warping (Bark transformation), critical-band integration, amplitude sensitivity variations with frequency, and conversion from loudness level to loudness. For each 10 ms segment of an utterance, a weighted spectral vector is computed via 15 critical band filters. The overall distortion, called Bark spectral distortion (BSD), is the average squared Euclidean distance between spectral vectors of the original and coded utterance. In tests with speech distorted by a modulated noise reference unit or coded at rates of 2.4-64 kb/s, the measure predicted mean opinion score (MOS) ratings are notably better than segmental SNR. The standard error in estimating MOS scores with the new measure was 0.2-0.3.>