Average of 250 measurements of the onset \(f_0\left(t\right)\)  and cessation \(f_c\left(t\right) = -f_o \left(t - \tau \right)\) response of the sensor at the maximum transmitted power, and the average of 50 measurements of an individual pyroelectric pulse generated using a 6 ms ultrasound burst at maximum power. The cessation response has been inverted and shifted by -τ so that its amplitude can be compared with that of the onset response.