A projector (transmitter) converts the energy from the power amplifier (generator) into an acoustic pressure output. Projectors are usually driven near their resonance frequencies where they provide the highest acoustic output.

Pressure is the force per unit area applied on a surface in a direction perpendicular to that surface.
Pressure can also be described as a form of potential energy in a fluid. The maximum pressure of the fluid medium obtained during propagation of an ultrasonic pulse.
The negative peak pressure is the peak rarefaction pressure attained during the negative portion of a propagating ultrasound pulse in a medium such as tissue.
Sound pressure can be measured using a microphone in air and a hydrophone in water. The SI unit for sound pressure is the Pascal.
Blood pressure is the pressure exerted by the blood on the walls of the blood vessels.

See also Rarefactional Pressure, Low Intensity Pulsed Ultrasound, and Projector.

The transmitter (see also projector) is the component of the ultrasound machine that creates the impulses sent to the transducer to generate the sound waves. Also called the pulser.

See also Transmit Voltage Response and Transmit Current Response.