Abstract: A measuring device for checking the tightness of an ear impression mold serving as pattern for the production of an otoplastic and/or of an otoplastic inserted in the auditory passage of an ear through which an air pressure deviating from the air pressure prevailing on the outside can be produced, via an air permeable connection, in the inner space defined by the ear drum and the ear impression or otoplastic. Through the device changes in the generated deviating air pressure can be measured. The air permeable connection is connected to a pump serving for the generation of the deviating air pressure via a pressure chamber whose volume is a multiple of the volume of the inner ear space. A control circuit presetting the timing of the pumping and measuring process is provided. The device is insensitive to differences in the volume of the inner ear space and produces reproducible test results which reliably indicate the quality of the ear impression of otoplastic.