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Evaluation of the impact of noise metrics on tiltrotor aircraft designA subjective noise evaluation was conducted in which the test participants evaluated the annoyance of simulated sounds representative of future civil tiltrotor aircraft. The subjective responses were correlated with the noise metrics of A-weighted sound pressure level, overall sound pressure level, and perceived level. The results indicated that correlation between subjective response and A-weighted sound pressure level is considerably enhanced by combining it in a multiple regression with overall sound pressure level. As a single metric, perceived level correlated better than A-weighted sound pressure level due to greater emphasis on low frequency noise components. This latter finding was especially true for indoor noise where the mid and high frequency noise components are attenuated by typical building structure. Using the results of the subjective noise evaluation, the impact on tiltrotor aircraft design was also evaluated. While A-weighted sound pressure level can be reduced by reduction in tip speed, an increase in number of rotor blades is required to achieve significant reduction of low frequency noise as measured by overall sound pressure level. Additional research, however, is required to achieve comparable reductions in impulsive noise due to blade-vortex interaction, and also to achieve reduction in broad band noise.
Document ID
Document Type
Contractor Report (CR)
Sternfeld, H.
(Boeing Defense and Space Group Philadelphia, PA, United States)
Spencer, R.
(Boeing Defense and Space Group Philadelphia, PA, United States)
Ziegenbein, P.
(Boeing Defense and Space Group Philadelphia, PA, United States)
Date Acquired
September 6, 2013
Publication Date
November 1, 1995
Subject Category
Report/Patent Number
NAS 1.26:198240
Accession Number
Funding Number(s)
PROJECT: RTOP 538-07-15-10
Distribution Limits
Work of the US Gov. Public Use Permitted.
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