Experiments in External Noise Reduction of a Small Pusher-Type Amphibian Airplane
Abstract
The work reported is part of a program the objective of which is to find practicable ways of reducing the external noise level of light airplanes. This report covers noise measurements on a representative pusher-type amphibian airplane. The work supplements earlier work by the Aeronautical Research Foundation on the external noise of tractor-type airplanes. Modifications of the pusher-type airplane and noise-measurement procedures used for the present work were similar to those used for the earlier noise study of the tractor-type airplane. Tests were made (1) with a standard pusher-type airplane; (2) with the same airplane using a four-bladed propeller; (3) with a modified version of the airplane using a geared engine and four-bladed propeller but no exhaust muffler; and (4) with a modified version of the airplane using a geared engine, exhaust muffler, and propellers varying in number of blades from three to eight. Tests were also made on the eight- bladed configuration of the geared and muffled airplane with the muffler relocated so that the exhaust did not pass through the propeller. For all configurations these tests included sound-level recordings of take-offs and of overhead flights at 100- and 500-foot altitude. They also included analyses of sound-frequency components with the air-plane on the ground from a distance of 50 feet and at various positions around the airplane. For some of the configurations sound-level recordings were made for flights at 500-foot altitude passing 3000 feet away. These measurements from 3000 feet away were also made for a standard tractor-type airplane. Finally, frequency analyses were made for the noise of one of the modified configurations of the pusher-type airplane during a flight passing 3000 feet away. Valuable information was obtained during this study concerning methods of external-noise measurement and interpretation of such measurements.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jun 01, 1952
- Accession Number
- ADA377112
Entities
People
- John P. Roberts
- Leo L. Beranek
Organizations
- National Aeronautics and Space Administration