Abstract: A system (400) for reducing non-acoustic noise includes a primary sensor (420), at least one secondary sensor (410), a filter (415), and a summation unit (425). The primary sensor (420) measures pressure and produces a primary pressure signal. The at least one secondary sensor (410) measures pressure and produce a secondary pressure signal. The filter (415) processes the secondary pressure signal to produce a filtered pressure signal. The summation unit (425) subtracts the filtered pressure signal from the primary pressure signal to reduce non-acoustic noise in the primary pressure signal.

Abstract: The disclosure describes techniques for determining the response characteristics of a system. One such technique includes applying a series of M vector probe input signal sets of a form {overscore (V)}m x(t) to the system, wherein {overscore (V)}m is an m-th column of a matrix V and x(t) is a scalar input signal. The response signals {overscore (y)}t are measured and a single-input system {overscore (F)}m(z) is determined by considering the approximate relationship {overscore (y)}z?{overscore (F)}m(z)x(z), where {overscore (F)}m(z) is an m-th column of a matrix F(z). The system characteristics can be determined from the relationship H(z)=F(z)V?1, where V?1 denotes the right-matrix-inverse of the matrix V. The matrix V may be a matrix with mutually orthogonal rows, or may have entries consisting of plus one and minus one values, or may be a portion of a Hadamard matrix.

Abstract: Systems and methods for designing or determining parameters for a system are disclosed. These systems and methods exploit the Tensor Convolution Block Toeplitz (TCBT) structure involved in certain systems wherein a symmetric positive definite linear system of equations needs to be solved in the design or determination of the parameters for the system. Further, these methods and systems employ a TCBT-PCG process that uses a fast matrix-vector multiply in order to improve the computational efficiency in the design or determination of these system parameters.

Abstract: In the control system disclosed herein, multiple input data streams are processed or filtered to generate multiple output streams by a filter which combines efficient batch processing of a fixed number of older input samples with immediate direct processing of a varying number of current samples thereby to generate multiple output data streams which are based on essentially current input data as well as older input data reaching back for a time interval which varies periodically.

Abstract: A code signal representing a sequence of code symbols carrying digital information is generated with the frequency components of the code signal being essentially confined to a preselected signalling band lying within the bandwidth of an audio signal within which the code signal is to be embedded. The audio signal is continuously frequency analyzed over a frequency band encompassing the signalling band and the code signal is dynamically filtered as a function of the analysis thereby to provide a modified code signal with frequency components which are, at each time instant, essentially a preselected small proportion of the levels of the corresponding audio signal frequency components. Accordingly, the modified code signal can be combined with the audio signal to obtain a composite audio signal which is not readily distinguishable from the original audio signal by listening.