Abstract: A hearing aid with digital, electronic compensation for acoustic feedback includes a microphone, a preamplifier, a digital compensation circuit and output amplifier and a transducer. The digital compensation circuit includes a noise generator for the insertion of noise, and an adjustable, digital filter for the adaptation of the feedback signal. The adaptation takes place using a correlation circuit which includes a digital circuit to carry out a statistical evaluation of the filter coefficients in the correlation circuit, and changes the feedback function in accordance with this evaluation.

Abstract: A device for a battery chamber (2) in a hearing aid (1) with replaceable battery (3) comprises a locking device for blocking the battery chamber. The locking device comprises a displaceable pin, which can be maneuvered through an opening (7) in the battery chamber by means of a pointed or thin object, e.g. a mandrel-shaped tool or the like.

Abstract: A protection element for the sound conduction channel (6) on an all-in-the-ear hearing aid (1) with a hearing aid housing (2) arranged to suit the user's auditory canal comprises an exchangeable filter element (3) which is snapped firmly on a sound conduction tube (5) which is disposed and secured in the hearing aid's sound conduction channel (6). The filter element (3) has a number of sound conduction openings (12). The invention also relates to a tool and a dispenser for use in the exchanging of the filter element (3).

Abstract: The invention relates to the measuring of sound pressure levels in the auditory canal of a person in connection with the fitting of a hearing aid. An apparatus for this purpose comprises a measuring probe (1) which is introduced into the auditory canal, a microphone (6) coupled to the measuring probe (1), a data processing unit (14) with display (15) and printer (15'), a reference microphone (8) and a source of sound (10). In order to be able to position the measuring probe (1) precisely in the auditory canal, the probe is configured with means for measuring the distance from the free end of the probe to the ear drum which employs either sound, electromagnetic waves or light.

Abstract: An electronic coupler for a microtelephone set (14, 31) for the coupling of an amplifier (2) in a telephone line (33a) to an operating position in a telephonist-operated switchboard with automatic call distributor comprises a coupling circuit (1) with a field-effect transistor which is coupled in parallel across the amplifier (2) in such a manner that, when the supply current (E+) is coupled to the amplifier (2), it has great impedance against incoming A.C. signals in the audio frequency range, for example a ringing signal, whereby the line (29a, 29b) is connected to the telephone cartridge (14) via the amplifier (2), and also that the coupler (1) has low impedance against incoming A.C. signals when the supply current (E+) is not coupled to the amplifier (2), so that the line (29a, 29b) is coupled (37) around the amplifier (2) and connected directly to the telephone cartridge (14).

Abstract: A hook shaped part (2) for a behind the ear hearing aid. The hook shaped part is hollow and at one end (5) formed to be connected to an acoustic output from the upper front end of the hearing aid case (1) and serving to transmit sound from the hearing aid in the direction of the ear, normally through a tube (3) and an ear plug (4), and also serving to support the hearing aid upon the outer ear. In the hook shaped part there is, at the end (8) furthest from the hearing aid included an acoustic filter (9). The hook shaped part (2) has, in the direction away from the hearing aid a channel (6) of increasing cross sectional area. Through the form of the channel (6) is obtained a suppression of resonant phenomena in the tube (3) and the frequency response is made independent of the length of this tube.