Ground effects on aircraft noise

A flight experiment was conducted to investigate air-to-ground propagation of sound near grazing incidence. A turbojet-powered aircraft was flown at low altitudes over the ends of two microphone arrays. An eight-microphone array was positioned along a 1850 m concrete runway. The second array consisted of 12 microphones positioned parallel to the runway over grass. Twenty-eight flights were flown at altitudes ranging from 10 m to 160 m. The acoustic data recorded in the field reduced to one-third-octave band spectra and time correlated with the flight and weather information. A small portion of the data was further reduced to values of ground attenuation as a function of frequency and incidence angle by two different methods. In both methods, the acoustic signals compared originated from identical sources. Attenuation results obtained by using the two methods were in general agreement. The measured ground attenuation was largest in the frequency range of 200 to 400 Hz. A strong dependence was found between ground attenuation and incidence angle with little attenuation measured for angles of incidence greater than 10 to 15 degrees

An Edition and Study of the Old English \u3cem\u3eSeasons for Fasting\u3c/em\u3e

This dissertation is an edition and study of the Old English Seasons for Fasting. Seasons in interesting to the student of Old English for several reasons: it is the longest regularly stanzaic poem in OE; its English stand on the Ember fast controversy and its attack on lax priest are atypical of OE verse as is the poem\u27s intended lay audience. The dissertation is in three sections: Chapter I introduces and describes the extant text (ff. 257r-260v, British Library MS. Add. 43703), discusses the school of composition, and provides new support for Wulfstan\u27s influence on the poem, describes the language of the poem, provides analyses of the style and the historical and poetic contexts of the poem. Chapter II consists of the text of Seasons for Fasting (based on British Library MS. Add. 43703), textual notes indicating the readings of all other editors, and a translation (the first in English). Chapter III is a commentary keyed to the lines of the poem. The commentary notes relevant criticism on difficult or interesting sections of the poem and offers several new readings

Position location and data collection system and method Patent

Development of telemetry system for position location and data acquisitio

Noise reduction studies for the OV-1 airplane

A study has been conducted to define possible modifications to the OV-1 aircraft to reduce its aural detection distance. This effort involved documenting the noise characteristics of the airplane, devising modifications to reduce the noise, estimating the reduction in detection distance, and evaluating aircraft performance as a result of these modifications. It was found that the main noise source on this aircraft is the propeller and hence modifications only to the propeller and the propeller drive system are proposed. Modifications involving only the propeller are noted to involve no increase in weight but they result in only a modest decrease in aural detection distance. In order to obtain substantial decreases in aural detection distance, modifications involving changes both to the propeller and the engine-propeller gearing are required

Noise measurement evaluations of various takeoff-climbout profiles of a four-engine turbojet transport airplane

Noise measurement evaluations of various takeoff-climbout profiles of four engine turbojet transport airplan