Acoustic feedbacks can be caused by the aeration channel (5) that is present in hearing aid devices (2) wearable in the ear or hearing aid devices having an otoplastic wearable in the ear. In order to avoid this, it is provided that the aeration channel be subdivided into at least a first and a second sub-region, whereby the sub-region (5A) that is proximal when the hearing aid device (2) is worn or when the otoplastic is worn comprises a small cross-sectional area and a great length compared to the distal, second sub-region (5B).