Comparison of a Passive and Active Notch Filter for Noise Reduction in Airborne Communications.
Abstract
The high noise environment present in a military helicopter creates two undesirable effects: (1) aviator hearing loss, and (2) reduced intelligibility. The noise environment studied in this report is the one which the pilot and copilot experienced on board the CH-47 (CHINOOK) helicopter. A detailed analysis of this noise reveals that it consists of several high-amplitude peaks within the audio frequency range. One approach to eliminating these peaks, and thus reducing the amount of noise reaching the aviators ears, is through the use of an electrical filter installed in the aircraft communications system. The 'ideal' filter for this purpose would be one that attenuates those frequencies at which peaks exist, and at the same time conserves as much of the audio frequency spectrum as possible. This latter requirement is necessary for good intelligibility of the overall communications system. The report gives a comparison of two different electrical filters. One is a passive device and is presently in use in each CH-47 in the Army's inventory. The other is a new state-of-the-art active traveling notch filter. The potential application of the active filter is discussed.
Document Details
- Document Type
- Technical Report
- Publication Date
- Sep 01, 1975
- Accession Number
- ADA015016
Entities
People
- John L. Politis
Organizations
- United States Army Communications-Electronics Command