A method for the automatic adjustment of the operating-frequency operating point of an ultrasonic detection device comprising an ultrasonic transmitter and an ultrasonic receiver and an acoustic transmission channel therebetween, wherein, in said method, - the driving frequency of the ultrasonic transmitter is changed at intervals, wherein the driving frequency during any one of the plurality of intervals has a value and in an interval following said interval has another value differing from said value, - the strength of the signal received by the ultrasonic receiver is determined, wherein changes in the strength of the received signal are detected in magnitude and sign by comparing the strength of the received signal determined in an interval to the strength of the received signal determined in a subsequent interval, - the driving frequency of the ultrasonic transmitter is varied for an interval in dependence on a change of the strength of the received signal that occurred temporally before this interval, wherein the variation of the driving frequency is performed with the same sign with which the strength of the received signal has changed, and - the driving frequency is varied until the strength of the received signal has reached a maximum or the driving frequency is varied in temporally successive intervals with alternating sign if the strength of the received signal remains essentially unchanged or the strength of the received signal also varies with alternating sign, whereby the operating point of the operating frequency of the ultrasonic detection device is set, - wherein the degree of a change in the driving frequency of the ultrasonic transmitter is selected to be proportional to the degree of the previous change in the strength of the received signal. - the driving frequency of the ultrasonic transmitter is changed at intervals, wherein the driving frequency during any one of the plurality of intervals has a value and in an interval following said interval has another value differing from said value, - the strength of the signal received by the ultrasonic receiver is determined, wherein changes in the strength of the received signal are detected in magnitude and sign by comparing the strength of the received signal determined in an interval to the strength of the received signal determined in a subsequent interval, - the driving frequency of the ultrasonic transmitter is varied for an interval in dependence on a change of the strength of the received signal that occurred temporally before this interval, wherein the variation of the driving frequency is performed with the same sign with which the strength of the received signal has changed, and - the driving frequency is varied until the strength of the received signal has reached a maximum or the driving frequency is varied in temporally successive intervals with alternating sign if the strength of the received signal remains essentially unchanged or the strength of the received signal also varies with alternating sign, whereby the operating point of the operating frequency of the ultrasonic detection device is set, - wherein the degree of a change in the driving frequency of the ultrasonic transmitter is selected to be proportional to the degree of the previous change in the strength of the received signal.