ultrasonic frequency

Electronics can filter electrical signals, but can not remove ultrasonic frequencies already in the air.

The tiny people use ultrasonic frequencies, which to human ears sound like "yeek."

"The air molecules themselves convert this ultrasonic frequency back down to a frequency that can be heard."

This charge, of course, oscillates at the ultrasonic frequency.

Dragon Man is vulnerable to intense cold and certain ultrasonic frequencies.

The intensity of the pulse can be measured as a function of the ultrasonic frequency.

In the sphere of ultrasonic frequency the radiation is concentrated on the ship's propellers.

Go further up and you reach ultrasonic frequencies where the noise can be heard by dogs and not humans.

To achieve finer detail, animals would have to move up into ultrasonic frequencies, and a number of mammals have done just that.

The bat's ear is similar in design to ours, but with refinements which give it great sensitivity at ultrasonic frequencies.