Abstract: Systems and methods for providing an ultra-stable measurement of the density of a fluid/gas species such as ozone in a mixture. The technique is based on information extracted from multi-wavelength light absorption, at which the species exhibits different absorption properties (coefficient values). The technique provides real-time compensation for short- and long-term instability in the light source and detector, and for detectable changes in the optical characteristics of the cell, thus improving the accuracy of the measurement while making frequent zeroing of the instrument unnecessary. In addition, the invention provides a high-performance technique for measuring ultra-high ozone densities using absorption at the Chappuis band.

Abstract: In an adaptive subband excited transform speech encoding system, a range of quantizers are available and are dynamically selected for each window of speech. The quantizers designated for individual subbands are determined to minimize mean squared error distortion in the recreated signal while using no more than a predetermined number of quantization bits per window of speech.

Abstract: A method of encoding speech includes a limited search of a tree-code excitation codebook with a closed loop gain calculation for each test path under consideration. The gain calculation occurs when minimizing an error distance measurement between a synthetic signal defined by each test path being considered and the appropriate speech signal by optimizing a scaling factor of the synthetic signal. The encoding method achieves a significant reduction in computational complexity with minimal loss of performance.

Abstract: A comb filter minimizes framing noise resulting from block encoding of speech. The comb filter has both pitch and coefficients adapted to the speech data. Block boundaries may be centered on filter segments of a fixed duration.

Abstract: In a speech coding system, scale factors are generated and encoded for each of a plurality of subbands of a Fourier transform spectrum of speech. Based on those scale factors, the spectrum is equalized. Coefficients of a limited number of subbands determined by the scale factors are encoded. The number of bits used to encode each coefficient of each transmitted subband is determined by the scale factor for each subband. At the receiver, coefficients of subbands which are not transmitted are approximated by means of a list replication technique.