Frequency Analysis of Helicopter Sound in the AS332 Super Puma

Document type: Researchreports
Full text:
Author(s): Thomas L Lagö
Title: Frequency Analysis of Helicopter Sound in the AS332 Super Puma
Series: Research report
Year: 1996
Issue: 8
ISSN: 1103-1581
Organization: Blekinge Institute of Technology
Department: Dept. of Signal Processing (Institutionen för signalbehandling)
Dept. of Signal Processing S-372 25 Ronneby
+46 455 780 00
Authors e-mail:
Language: English
Abstract: This technical report describes a series of measurements performed on an AS332 Super Puma, MKII (HKP10) helicopter. The measurements are part of a research project, A New Generation Active Headsets and its Psychological Effects, financed by the KKS board (Board of Knowledge and Competence). The project participants are: Lindholmen Development, Hellberg Safety, Active Control and the University of Karlskrona/Ronneby. CelsiusTech has recently joined the project as an industrial partner. The Air Force base at F17 in Kallinge and the AMI group in Ronneby are involved as evaluation groups.
There are substantial noise levels in helicopters, especially at low frequency. These noise levels are normally not harmful to the ear. However, the low frequency content masks the speech. For this reason, pilots tend to set the intercom system at maximum sound level, producing
potentially damaging sound levels for the human ear. Dr. P-A Hellström at Lindholmen Development has measured almost 100 dBA inside the ear canal when the intercom system is in use. This high sound level exposes the ear to fatigue and hearing loss.
The background noise is the key reason for the problem, although it is not the key source of sound damage to the ear. The frequency content in the masking background sound is of great importance. It was thus important to investigate if the sound consisted of pure tones or if it was more broadband in nature. The dominant sound sources needed to be identified and the number of harmonics for each source established. It was also important to investigate if there was a strong connection between the structure borne and the air borne sound.
Subject: Signal Processing\Detection and Classification
URN: urn:nbn:se:bth-00036