A method for recognizing a gesture made outside a vehicle includes setting a frequency of an ultrasound based on a thickness of a vehicle shell of the vehicle and an attenuation coefficient of the vehicle shell, emitting a plurality of ultrasounds having the frequency outwardly from an inner side of the vehicle shell, receiving a plurality of reflected waves returned by an obstacle reflecting the plurality of ultrasounds, determining whether the obstacle is a hand according to time differences between emission times of the plurality of ultrasounds and reception times of the plurality of reflected waves corresponding to the plurality of ultrasounds, and recognizing the gesture of the hand in response to determining that the obstacle is the hand.

A method for recognizing a gesture made outside a vehicle includes setting a frequency of an ultrasound based on a thickness of a vehicle shell of the vehicle and an attenuation coefficient of the vehicle shell, emitting a plurality of ultrasounds having the frequency outwardly from an inner side of the vehicle shell, receiving a plurality of reflected waves returned by an obstacle reflecting the plurality of ultrasounds, determining whether the obstacle is a hand according to time differences between emission times of the plurality of ultrasounds and reception times of the plurality of reflected waves corresponding to the plurality of ultrasounds, and recognizing the gesture of the hand in response to determining that the obstacle is the hand.

A method, computer system, and a computer program product for environment monitoring. Exemplary embodiments may include emitting one or more soundwaves within an environment, detecting the emitted one or more soundwaves, and identifying motion of an object within the environment based on an analysis of the detected one or more soundwaves.

A method, computer system, and a computer program product for environment monitoring. Exemplary embodiments may include emitting one or more soundwaves within an environment, detecting the emitted one or more soundwaves, and identifying motion of an object within the environment based on an analysis of the detected one or more soundwaves.

A displacement detection device includes a transmitter, a receiver, and a controller configured or programmed to output a first transmission signal to the transmitter to transmit a modulated wave and acquire a responsive first reception signal in a first measurement period, extract first phase information indicating a phase defined in a correlation between a first transmission signal and a reception signal, output a second transmission signal to the transmitter and acquire a responsive second reception signal in a second measurement period after the first measurement period, extract second phase information indicating a phase defined in a correlation between the second transmission signal and reception signal, and detect a displacement of an object between the first and second measurement periods, depending on a difference between the first and second phase information.

A displacement detection device includes a transmitter, a receiver, and a controller configured or programmed to output a first transmission signal to the transmitter to transmit a modulated wave and acquire a responsive first reception signal in a first measurement period, extract first phase information indicating a phase defined in a correlation between a first transmission signal and a reception signal, output a second transmission signal to the transmitter and acquire a responsive second reception signal in a second measurement period after the first measurement period, extract second phase information indicating a phase defined in a correlation between the second transmission signal and reception signal, and detect a displacement of an object between the first and second measurement periods, depending on a difference between the first and second phase information.