Predicting the audibility and annoyance of unducted fan engines

Predictions of the prevalence of annoyance associated with aircraft noise exposure are heavily influenced by field studies conducted in urban airport neighborhoods. Flyovers heard in such relatively high ambient noise environments are composed in large part of high absolute level, broadband noise. In contrast, noise exposure created en route by aircraft powered by unducted fan engines is expected to be relatively low in level, but to contain prominent low frequency tonal energy. These tones will be readily audible in rural and other low ambient noise environments. The annoyance of noise intrusions of low absolute level has been shown to be closely related to their audibility. Thus, one way to predict the annoyance of en route noise generated by unducted fan engines is to estimate its audibility relative to that of conventionally powered aircraft in different ambient noise environments. This may be accomplished by computing the audibility of spectra produced by an aircraft powered by unducted fan engines and comparing predicted probabilities of annoyance for them with those of conventionally powered transport aircraft

Study of the effects of the Doppler shift on perceived noisiness

Judgment of effects of Doppler shifts on perceived noisiness of aircraft made by subjects in anechoic chambe

Community sensitivity to changes in aircraft noise exposure

Interviews were conducted in the vicinity of Burbank Airport during a four month period during which a counterbalanced series of changes in aircraft noise exposure occurred due to runway repairs. Another interview was undertaken approximately one year after completion of the initial runway repairs. Noise measurements were made in conjunction with administration of a brief questionnaire to a near exhaustive sample of residents in four airport neighborhoods. The magnitude and direction of change of annoyance with aircraft noise exposure corresponded closely to the actual changes in physical exposure. Estimates were made of time constants for the rate of change of attitudes toward aircraft noise

Use of Airport Noise Complaint Files to Improve Understanding of Community Response to Aircraft Noise

This study assessed the feasibility of using complaint information archived by modem airport monitoring systems to conduct quantitative analyses of the causes of aircraft noise complaints and their relationship to noise- induced annoyance. It was found that all computer-based airport monitoring systems provide at least rudimentary tools for performing data base searches by complainant name, address, date, time of day, and types of aircraft and complaints. Analyses of such information can provide useful information about longstanding concerns, such as the extent to which complaint rates are driven by objectively measurable aspects of aircraft operations; the degree to which changes in complaint rates can be predicted prior to implementation of noise mitigation measures; and the degree to which aircraft complaint information can be used to simplify and otherwise improve prediction of the prevalence of noise-induced annoyance in communities

Comparison of methods of predicting community response to impulsive and nonimpulsive noise

Several scientific, regulatory, and policy-coordinating bodies have developed methods for predicting community response to sonic booms. The best known of these is the dosage-response relationship of Working Group 84 of the National Academy of Science's Committee on Hearing, Bioacoustics and Biomechanics. This dosage-response relationship between C-weighted DayNight Average Sound Level and the prevalence of annoyance with high energy impulsive sounds was derived from limited amounts of information about community response to regular, prolonged, and expected exposure to artillery and sonic booms. U.S. Army Regulation 201 adapts this approach to predictions of the acceptability of impulsive noise exposure in communities. This regulation infers equivalent degrees of effect with respect to a well known dosage-response relationship for general (nonimpulsive) transportation noise. Differences in prevalence of annoyance predicted by various relationships lead to different predictions of the compatibility of land uses with sonic boom exposure. An examination of these differences makes apparent several unresolved issues in current practice for predicting and interpreting the prevalence of annoyance due to sonic boom exposure