What is the duration of helicopter sound?
It is important to keep in mind that typical heliport activity creates an extremely brief sound. The entire sound event lasts for only approximately 45 seconds either on landing or takeoff. At any one point along the flight route, providing the observer is close enough to hear or notice it, the helicopter will typically be heard only for 20 seconds or less. This compares very favorably with sounds already found in most neighborhoods. This is quite unlike other transportation uses such as streets, highways, interstate road systems, commuter and freight railroads and certain waterways, where the sound production is almost constant in many circumstances.
