Power toothbrush with a modulated drive signal

A power toothbrush, comprising:

• a handle portion;
• a brushhead assembly having a set of bristles at a distal end thereof;
• a drive system responsive to a drive signal for moving the set of bristles with a motion having a frequency in the sonic range and an amplitude in a range to produce clinically effective cleaning of a user's teeth during a brushing event;
• and
• a modulation system that comprises a drive signal source, a modulation signal source and an audio mixer coupled to the drive signal source and the modulation signal source for outputting a combined modulation drive signal for changing at least one of a frequency or duty cycle of the drive signal, wherein responsive to the combined modulation drive signal, the drive system further moves the set of bristles for producing at least one of a cognitive stimulation or relaxation effect in addition to the clinically effective teeth cleaning, wherein (i) for the cognitive stimulation effect, the combined modulation drive signal increases in frequency from a start of the brushing event to an end of the brushing event, and (ii) for the cognitive relaxation effect, the combined modulation drive signal decreases in frequency between the start and end of the brushing event.