SLASEC8B February 2017 – January 2019 PGA460-Q1
When a voltage is applied to piezoelectric ceramics, mechanical distortion is generated according to the voltage and frequency. The mechanical distortion is measured in units of sound pressure level (SPL) to indicate the volume of sound, and can be derived from a free-field microphone voltage measurement using Equation 9.
The SPL does not increase indefinitely with the driving voltage. After a particular driving voltage, the amount of SPL that a transducer can generate becomes saturated. A transducer is given a maximum driving voltage specification to indicate when the maximum SPL is generated. Driving the transducer beyond the maximum driving voltage makes the ultrasonic module less power-efficient and can damage or decrease the life expectancy of the transducer.
For the detailed procedure on measuring the SPL of a transducer, refer to PGA460 Ultrasonic Module Hardware and Software Optimization.