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.