Abstract: An identification method and apparatus in a sound-reproduction system, in which an electrical calibration signal is created, an audio signal is created in the loudspeaker from the calibration signal, the response of the audio signal is measured and analysed, and the system is adjusted on the basis of the measurement results. A light signal is created in the loudspeaker with the aid of a centralized control system, in order to indicate visually the loudspeaker that is the subject of the calibration.

Abstract: The present invention relates to a method for designing a modal equalizer (5) for a low frequency audible range, typically for frequencies below 200 Hz for a predetermined space (1) (listening room) and location (2) (location in the room) therein, in which method modes to be equalized are determined at least by center frequency and decay rate of each mode, creating a discrete-time description of the determined modes, and determining equalizer filter coefficients on the basis of the discrete-time description of the determined modes, and forming the equalizer (5) by means of a digital filter by defining the filter coefficients on the basis of the properties of the modes.

Abstract: A method and apparatus for attenuating acoustic reflections related to sound radiated by a loudspeaker in an acoustic space. According to the method, at least one cancelling loudspeaker is used for radiating a canceling sound in the space. The signal required for producing the cancelling sound is sampled from the sound reproduction apparatus prior to the processing of the original sound signal for emission into the acoustic space. The sample signal is low-pass filtered, delayed, amplified and inverted prior to being taken to the cancelling loudspeaker. The sound reproduction apparatus includes a signal sampling device, control devices, and at least one cancelling loudspeaker for radiating the cancelling sound.

Abstract: A digital audio receiver stores received frames temporarily for decoding and error concealment. A reconstructing block (14) in the decoder reads stored frames using a read window (43) wherein the latest received frame (+cnnxt) is undecoded. Decoding is carried out in stages so that the correctness of the current frame (0) is examined and possible errors are concealed using corresponding data of other frames in the window. Detection of errors is based on checksums (19, 26) and allowed values of bit combinations in certain parts of the frame. In addition, the receiver maintains an estimate (60) for the signal's bit error ratio and uses it to control the operation of the error concealment algorithm.

Abstract: The present invention concerns the reduction of vibrations of a loudspeaker enclosure caused by the mechanical vibrations of the dynamic loudspeaker element by virtue of attaching one or more additional masses to the loudspeaker driver unit using elastic and lossy means. The masses with their elastic attachments dimensioned according to the present invention resonate at frequencies excited by the vibrations of the loudspeaker element at frequencies where the reduction of the amount of vibration is desired. The magnitude of vibration coupled to the enclosure of a loudspeaker modified according to the present invention is significantly smaller than that of a conventional loudspeaker. Furthermore, it is technically and economically advantageous to implement the reduction of mechanical vibrations according to the present invention.