Abstract: In an audio processing arrangement (2) input signals from a plurality of input sources (4,6) are weighted by weighting factors x and y using weighting elements (10, 12). The weighted input signals are combined to a combined signal by an adder (18). The output signal of the adder (18) constitutes the output of the audio processing arrangement. In order to pronounce the signal with the strongest signal, the weighting coefficients (x,y) are controlled to maximize the output signal of the adder (18) under the constraint that the sum of the squares of the weighting coefficients is equal to a constant.

Abstract: In an audio processing arrangement (2) input signals from a plurality of input sources (4,6) are weighted by weighting factors x and y using weighting elements (10, 12). The weighted input signals are combined to a combined signal by an adder (18). The output signal of the adder (18) constitutes the output of the audio processing arrangement. In order to pronounce the signal with the strongest signal, the weighting coefficients (x,y) are controlled to maximize the output signal of the adder (18) under the constraint that the sum of the squares of the weighting coefficients is equal to a constant.

Abstract: In a video conferencing system, camera position means are used to point the camera to a speaking person. To find the correct direction for the camera, a system is required that determines the position from which the sound is transmitted. This can be done by using at least two microphones receiving the speech signal. By measuring the transmission delay between the signals received by the microphones, the position of the speaker can be determined. According to the present invention, the delay is determined by first determining the impulse responses (h1) and (h2) and subsequently calculating a cross correlation function between the impulse responses (h1) and (h2). From the main peak in the cross correlation function, the delay value is determined.

Abstract: In an acoustic echocanceller (6), an estimate of an echo signal is determined by an adaptive filter (10) and is subtracted from the input signal by a subtracter (14). The spectrum estimator (12) determines the frequency spectrum of the estimate of the echo signal, and the filter (16) filters the output signal of the subtracter (14) with a filter having a transfer function dependent on the spectrum determined by the estimator (12). The use of this combination results in a substantial improvement of the suppression of the echo signal.

Abstract: In an acoustic echocanceller (6), an estimate of an echo signal is determined by an adaptive filter (10) and is subtracted from the input signal by a subtracter (14). The spectrum estimator (12) determines the frequency spectrum of the estimate of the echo signal, and the filter (16) filters the output signal of the subtracter (14) with a filter having a transfer function dependent on the spectrum determined by the estimator (12). The use of this combination results in a substantial improvement of the suppression of the echo signal.

Abstract: A signal amplification system wherein a signal coming from a microphone is applied to a loudspeaker via a signal processing system. The signal processing system includes an estimator for estimating the transfer function from the loudspeaker to the microphone. The equalizer is set to a transfer function that is reciprocal to the transfer function from the loudspeaker to the microphone to equalize the transfer function from the microphone to the listeners. The estimator may include an adaptive filter which has a transfer function that approaches the transfer function from the loudspeaker to the microphone.

Abstract: A topological network, comprising a set of 0-cells (nodes) (28, 29) interconnected by a set of 1-cells (aa, bb, . . . , gg).sub.1 is divided into sections (E, F, G) corresponding to discrete parcels of data for storage in a mass memory such as a CD-ROM. A boundary node (28, 29) is defined at each point where the network traverses a boundary between sections. The parcel of data for a given section includes a chain list record for each 1-cell in the section, which chain list record generally refers directly (TP) to a further 1-cell in the network terminating at the same node. However, no chain list record refers directly to a 1-cell outside the section of the network to which the data parcel relates. An indirect reference (0-C') across the section boundary can be made easily, while an overall saving in data volume is obtained compared with a known method.

Abstract: In a signal amplifier system, a microphone (2) is connected to an echo canceller (16) via a decorrelator (6). The output signal of the echo canceller (16) is amplified by an amplifier (14) and fed to a loudspeaker (18). The echo canceller (16) is included to avoid instability caused by undesired feedback of the signal coming from the loudspeaker (18) through a feedback path (11). To improve the stabilizing effect of the echo canceller (16), the decorrelator (6) is included for decorrelating the signal coming from the microphone (2) and the signal transmitted by the loudspeaker (18).

Abstract: A known cross-coupled adaptive noise cancelling arrangement uses an adaptive noise filter and an adaptive cross-talk filter in a feedback loop for cancelling correlated noise at a primary signal input and reference input. This known cross-coupled ANC does not operate satisfactorily, particularly not for acoustic noise cancellation. This leads to reverberant-like sound signals, in particular in a typical office room with remote noise sources. A different configuration of a cross-coupled adaptive noise cancelling arrangement gives rise to a better performance. The adaptive cross-talk filter is now split into a pre-filter section and an adaptive filter section, the sections using different input signals.

Abstract: A noise reduction system and device, and a mobile radio station. Known is a combined Zelinski-spectral subtraction system (1) for noise reduction in a combined speech signal (a(t)) in which signals are recorded with a plurality of microphones (5, 6, 7), using a Wiener filter (10) for estimation of the combined speech signal (a(t)'). In the known system (1) sums and differences of all combinations of speech signals are formed, it being assumed that the differences comprise noise only. Furthermore, a two stage estimation process is carried out, giving rise to considerable estimation errors. An alternative combined Zelinski-spectral subtraction system (1) is proposed, giving rise to fewer estimation errors and being more efficient from a computational point of view. In the Zelinski system, spectral subtraction is carried out on a combined cross spectrum (.PHI..sub.cc).

Abstract: A conference system comprises speaker units (12) coupled to a central unit (14). The speaker unit (12) comprises an echo canceller (20) with an adaptive filter (38) having an impulse response of comparatively short duration. In a speech pause of the user of the speaker unit (12) the common listening signal (LS) of the conference system is applied to the loudspeaker (18). Of the sounds then picked up by the microphone (16) only those sounds are compensated which are produced by the loudspeaker (18) and which reach the microphone (16) directly and which reach the microphone (16) indirectly via reflections from nearby objects. These sounds have a comparatively short impulse response time and enable a comparatively simple adaptive filter (38) to be used. The other sounds picked up by the microphone (16) reach the microphone (16) via reflections from the walls of the conference space (10) in which the conference system is situated. The other sounds have a comparatively long impulse response time.

Abstract: An echo canceller for use in send/receive apparatus includes a frequency-domain adaptive filter which provides filter parameters to a time-domain programmable filter. The programmable filter produces a signal y(k) which is an estimate of the echo signal produced by acoustic coupling between a loudspeaker in the received path and a microphone in the send path. By subtracting this estimate from the signal produced in the send path, an output signal r(k) is obtained from the send path which is essentially free of echoes. An accurate estimate of the echo signal cannot be obtained if a send signal is present at the input of the send path. Therefore, detecting means in the adaptive filter detects whether such a send signal is present and in that case blocks the transfer of filter parameters from the adaptive filter to the programmable filter. Erroneous modification of the estimated echo signal is thereby avoided.

Abstract: A method of storing in a memory digital data representing a topological network having a set of nodes (0-cells), segments (1-cells), and areas (2-cells) within concatenated 1-cells. For each 1-cell there are stored an associated first 0-cell and second 0-cell and also a thread pointer assigned to the 0-cells. The thread pointer of an 0-cell indicates the next-following 1-cell obtained by rotating the 1-cell in question in a predetermined direction of rotation around such 0-cell. For finding a 2-cell, use is made of a first 1-cell and the thread pointer associated with one of its 0-cells is followed after which, starting from the newly found 1-cell, each time the thread pointer of the opposite 0-cell is used until the first 1-cell is found again.

Abstract: A database is stored in a mass memory. For this purpose, it is first divided into main cells and then into base cells according to a predetermined regular division pattern. Each base cell is then checked to see whether its data content is sufficient to occupy substantially completely a storage parcel having a predetermined capacity. If this is the case, the base cell is thus accommodated in a storage parcel; if this is not the case, adjacent base cells are grouped until a storage parcel is occupied substantially completely. The operation of addressing a storage parcel is effected by the use of a main cell table in which address pointers are stored, each of which points to a base cell table. In the base cell table, an index is given for each base cell and this index indicates in which storage parcel the relevant base cell is accommodated.

Abstract: In an acoustic echocanceller (6), an estimate of an echo signal is determined by an adaptive filter (10) and is subtracted from the input signal by a subtracter (14). The spectrum estimator (12) determines the frequency spectrum of the estimate of the echo signal, and the filter (16) filters the output signal of the subtracter (14) with a filter having a transfer function dependent on the spectrum determined by the estimator (12). The use of this combination results in a substantial improvement of the suppression of the echo signal.