Abstract: An ultrasonic sensing method and an ultrasonic sensing device are provided. The ultrasonic sensing device includes a microprocessor, a signal-driving module and a transducer module. The microprocessor generates a first driving signal with a first frequency to the signal-driving module. The signal-driving module drives the transducer module to emit a first sensing signal to a target object in response to the first driving signal. Then, a first echo signal received by the transducer is transmitted to the microprocessor to calculate a first time of flight. In a similar manner, a second time of flight is obtained based on a second driving signal with a second frequency. The microprocessor determines a final time of flight according to the first time of flight or the second time of flight.

Abstract: A signal decay time adjusting method is used in an ultrasonic transducer. Firstly, a first driving signal is generated by a pre-processing module. When the first driving signal is received, an ultrasonic transmitting/receiving module generates vibration and transmits a sensing wave according to the first driving signal. Then, the pre-processing module stops generating the first driving signal so that the vibration generated within the ultrasonic transmitting/receiving module is decayed as a decay signal. Then, a second driving signal is generated by the pre-processing module according to the first driving signal, and the second driving signal is transmitted to the ultrasonic transmitting/receiving module. When the second driving signal is received, the decay signal is offset according to the second driving signal, so that a decay time of the decay signal is shortened. When the sensing wave is reflected by an object, a reflective wave is received by the ultrasonic transmitting/receiving module.