Evaluation of Alternative Procedures for Atmospheric Absorption Adjustments during Noise Certification. Volume I. Analyses and Results
Abstract
The work reported here extends that in FAA-RD-77-167, December 1977 to the problem of adjusting actual aircraft noise 1/3-octave-band spectra measured at 0.5-s intervals. Test-day spectra are used to calculate PNL, PNLT, EPNL, AL, and SEL. The test-day spectrum at the time of PNLTM and at the time of ALM are adjusted to acoustical-reference conditions using the atmospheric- absorption method in American National Standard ANSI S1.26-1978 and applied, using measurements of air temperature and relative humidity at various heights above the ground, by integrating over the frequency range of the passband of ideal filters and by calculating the absorption at the exact band-center frequencies only. SAE ARP866A is also used with the vertical-profile temperature/humidity data and with data at 10 m to determine adjustments from test-to-reference conditions. The adjustment methods are applied to noise data from nine aircraft. Volume I describes the analyses and results of the study. Volume II presents the computer program that was developed and illustrates its use with a test case. Volume III presents tables of attenuation due to atmospheric absorption over a 300-m path. Attenuations were calculated using ANSI S1.26-1978 for pure tones at band-center frequencies and for three noise spectral slopes by a band-integration method, and using SAE ARP866A. For each of the five methods, the tables cover 34 air temperatures from 2 to 35 C, 10 relative humidities from 10 to 100 percent, and 24 nominal band-center frequencies from 50 to 10,000 Hz. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Oct 01, 1980
- Accession Number
- ADA111720
Entities
People
- Alan H. Marsh