  Polyvinylidene difluoride (PVDF) sensors are of interest to ultrasonic
applications due to their high sensitivity and efficient acoustic coupling to
the environment. PVDF sensors for scientific applications typically possess a
flat frequency response to faithfully reproduce spectral components of an
unknown source. However, in industrial sensing applications higher responsivity
is desirable even at the cost of decreased flatness in the spectral
responsivity. To better understand the trade-offs between intrinsic
responsivity and spectral response we examine four PVDF sensor variants for
spectral responsivity as a function of thickness and find that increased
responsivity is correlated with a strong non-linear frequency dependence.
