The 16-bit Timer TCA from ATtiny817 will sort out PWM pulses with a frequency of 40kHz. After passing the CCL and TCD logic mask process, the PWM pulses can switch the ultrasonic transceiver via a MOSFET to generate bursted ultrasonic waves. The ultrasonic waves will then propagate in the air until encountering any obstacles and reflecting back.
The PWM pulses drive the burst circuit shown above to generate waves with amplitude close to 20Vpp. See the measured PWM pulses in yellow and ultrasonic waves in green in the figure below.
The signal amplitude is given by the PWM. The PWM's duty cycle is set to 50%. The MCUSD16A40S12RO ultrasonic transducer emits ultrasonic waves into the air.