REDUCTEUR DE BRUIT

A.REDUCTEUR DE BRUIT.B.CARACTERISE EN CE QU'IL COMPORTE UN PREMIER CHEMIN DE SIGNAL AVEC UN AMPLIFICATEUR A GAIN VARIABLE 13 POUR AMPLIFIER UN SIGNAL AVEC UN GAIN REGLABLE ET UN DIFFERENTIATEUR 14 POUR DIFFERENTIER AU MOINS UNE PARTIE DU SIGNAL QUI TRAVERSE L'AMPLIFICATEUR A GAIN VARIABLE, UN MOYEN DE COMMANDE 11A, 19B DU GAIN DE L'AMPLIFICATEUR A GAIN VARIABLE, UN PREMIER MOYEN 15 RELIE AU PREMIER CHEMIN DE SIGNAL POUR DONNER UNE LIMITE SUPERIEURE AU GAIN APPLIQUE AU SIGNAL FOURNI AU CIRCUIT ET UN SECOND MOYEN 16 RELIE AU SECOND CHEMIN DE SIGNAL POUR FIXER UNE LIMITE INFERIEURE AU GAIN APPLIQUE AU SIGNAL FOURNI AU CIRCUIT.C.L'INVENTION S'APPLIQUE AUX REDUCTEURS DE BRUIT POUR LES APPAREILS D'ENREGISTREMENT ET DE REPRODUCTION DE SIGNAUX D'INFORMATION. A noise reduction circuit for use in an audio signal recording/reproducing apparatus is comprised of a first signal path including a voltage-controlled amplifier for amplifying a signal supplied thereto with controllable gain and a differentiating circuit for differentiating at least that portion of the signal passing through the voltage-controlled amplifier within the audio range; a level detecting circuit for controlling the gain of the voltage-controlled amplifier in response to the level of the signal passing through the voltage-controlled amplifier; a feedback resistor connected as a negative feedback path with the first signal path for providing an upper limit to the gain imparted to the signal supplied to the noise reduction circuit; a subtraction circuit for subtracting the negatively fed back signals from the signal supplied to the noise reduction circuit to produce an input signal for the first signal path; a second resistor or a low-pass filter connected as a positive feedforward path between the input of the noise reduction circuit and the output of the first signal path for providing a lower limit to the gain imparted to the signal supplied to the noise reduction circuit; and an anti-limiting circuit connected in parallel with the feedback resistor for compensating the signal supplied to the noise reduction circuit when the level of the signal is abruptly increased.