Disclosed is a disk recording and reproduction apparatus for recording andor reproduction of optical disks of multiple different formats impossible to record or reproduce with a single pickup. The oral appliance may have an electronic andor transducer assembly for receiving incoming sounds and transmitting processed sounds via a vibrating transducer element coupled to a tooth or teeth. The adaptive main filter is an adaptive filter for which the adaptation speed is proportional to a system noise estimate and the adaptation speed of the shadow filter is faster than the adaptation speed of the adaptive main filter.