Abstract: For processing a signal applied to an input of audio signal processing devices, for example a speech signal received via a microphone (2) in a speaker-identification or speech recognition system, the signal must have a specific level. For this purpose the signal is applied via an amplifier (4) with variable gain. Before processing begins, the gain is set to an initial value. During processing of the speech signal, it is checked, at regular time intervals, in which range of a plurality of predetermined amplitude ranges the amplified signal is situated, and whether overloading takes place and the frequency which the amplitude of the signal occurs in each of the amplitude ranges is counted. When the signal ends, the optimum gain setting is determined from the histogram of frequencies.

Abstract: The degree of mis-match which would be obtained between a test and a reference signal, for example speech signals, should their time-axes be subjected to that relative shift and/or distortion which is required to minimize the degree of mismatch is carried out by sampling the two signals at regular intervals and storing these samples in memories. All the samples of one signal are then read out in succession from one memory; each successive sample of the other signal is read out from the other memory, and the difference between each pair of samples is formed in a subtractor. Each difference value from the subtractor is added to the smallest of three quantities, X, Y and Z and the result stored in a register to form the new quantity X. This new quantity X is also stored in a further memory cyclically addressed in tandem with the memory 12.

Abstract: In a device for adjusting a movable electro-acoustic sound transducer, an optical duct is connected to the sound transducer which only allows an object, such as a display table or a data display unit, to be viewed completely in one specific position. This position is unambiguously reproducible and so is the position of the sound transducer or microphone relative to the mouth of the speaker. The optical duct may comprise diaphragms or a tube, possibly with intermediate walls, or a phase amplitude grating.The object may be a display unit and the device further comprises a device for generating variable data on the display. If used for speaker identification, the variable data generator projects consecutive instructions on the display so that, the speech recognition process is controlled automatically. The speaker to be identified is then required to keep his mouth in the correct position relative to the microphone.