  The velocity and pressure of an ultrasonic wave can be measured by an
electromagnetic hydrophone made of a thin wire and a magnet. The ultrasonic
wave vibrates the wire inside a magnetic field, inducing an electrical current.
Previous articles reported poor spatial resolution of comparable hydrophones
along the axis of the wire. In this study, submillimetric spatial resolution
has been achieved by using a tomographic method. Moreover, a physical model is
presented for obtaining absolute measurements. A pressure differential of 8%
has been found between piezoelectric and electromagnetic hydrophone
measurements. These characteristics show this technique as an alternative to
standard hydrophones.
