http://worldcat.org/entity/work/id/137297532

Interior Noise and Vibration Measurements on Operational Military Helicopters and Comparisons with Various Ride Quality Criteria

This paper presents physical measurements of the interior noise and vibration obtained within eight operational military helicopters. The data were analyzed and are presented in the following forms: noise and vibration spectra, overall root-mean-square acceleration levels in three linear axes, peak accelerations at dominant blade passage frequencies, acceleration exceedance data, and overall and A-weighted sound pressure levels. Peak acceleration levels were compared to the ISO 1-hr reduced comfort boundary, the fatigue decreased proficiency boundary, and the NASA discomfort criteria. The A-weighted noise levels were compared to the NASA annoyance criteria, and the overall noise spectra were compared to MIL-STD-1294 (Acoustical Noise Limits in Helicopters) . It is shown that specific vibration components at blade passage frequencies for several aircraft exceeded both the ISO reduced comfort boundary and the NASA passenger discomfort criteria. The A -weighted noise levels, corrected for SPH-4 helmet attenuation characteristics, exceeded the NASA annoyance threshold for several aircraft. The spectral components of the noise at cruise, corrected for helmet attenuation, fell within the limits of MIL-STD-1294 for all aircraft.

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