A physiological process for locating distant or invisible objects (as prey) by sound waves reflected back to the emitter (as a bat) from the objects.

An equivalent averaging time of less than 0.0001 seconds in the detector of a sound level meter.

The measurable height of an aircraft above the actual terrain.

The science of sound, including its production, transmission, and effects.

The distance Above Ground Level.

The movable areas of a wing form that control or affect the roll of an aircraft by working opposite one another -- up-aileron on the right wing and down-aileron on the left wing.

The instantaneous magnitude of an oscillating quantity such as sound pressure. The peak amplitude is the maximum value.

Airport Noise and Capacity Act of 1990, prohibits U.S. airports from adopting overly restrictive or outright punitive anti-noise ordinances.

Airport Noise and Capacity Act of 1990, prohibits U.S. airports from adopting overly restrictive or outright punitive anti-noise ordinances.

An instrument or device that measures the air speed of an aircraft through an air mass.