Flight Investigation of Cabin Noise Control Treatments for a Light Turboprop Aircraft

Wilby, J. F.; Oneal, R. L.; Mixson, J. S.

doi:10.4271/850876

Cited by 1 publication

(2 citation statements)

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“…13. Then, the insertion losses were averaged over all locations (2)(3)(4)(5)(6) in the cabin and compared with insertion losses measured at location 1 in the cockpit (Fig. 14).…”

Section: Treatment Insertion Loss Insertion Loss Spectramentioning

confidence: 99%

“…2 ' 3 The problems were attributed, at least in part, to data variability from flight to flight, with the result that the acoustic performance of the treatment could not be evaluated accurately for low-order harmonics of the propeller blade passage frequency. A second series of flight tests was conducted with the objective of improving the understanding of the problems and exploring methods of alleviating them.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Measurements of propeller noise in a light turboprop airplane

Wilby¹,

Wilby²

1989

Journal of Aircraft

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In-flight acoustic measurements have been made on the exterior and interior of a twin-engined turboprop airplane under controlled conditions to study data repeatability. It is found that the variability of the harmonic sound pressure levels in the cabin is greater than that for the exterior sound pressure levels, typical values for the standard deviation being +2.0 and -4.2 dB for the interior vs +1.4 and -2.3 dB for the exterior. When insertion losses are determined for acoustic treatments in the cabin, the standard deviations of the data are typically ±6.5 dB. It is concluded that factors such as accurate and repeatable selection of relative phase between propellers, controlled cabin air temperatures, installation of baseline acoustic absorption even for "untreated" configurations, and measurement of aircraft attitude should be considered in order to reduce uncertainty in the measured data.

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“…13. Then, the insertion losses were averaged over all locations (2)(3)(4)(5)(6) in the cabin and compared with insertion losses measured at location 1 in the cockpit (Fig. 14).…”

Section: Treatment Insertion Loss Insertion Loss Spectramentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%