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The subjective response of humans to jet noises was studied to determine the relative difference in subjective annoyance levels produced by different jet engine configurations. The noises studied were representative of jet airplane ground and fly‐over operations. Further testing was carried out to determine the relative annoyance properties of random noise spectra which were characterized by the presence of outstanding single frequency tones. Emphasis was placed on discovery of the relationships between “spike” frequency, “spike” amplitude, and over‐all sound pressure level. The results of this program are presented with comments on their use as a basis for more extensive programs of this nature.

The R‐6 Research Committee of the Society of Automotive Engineers was organized in February 1968 for the purpose of developing an accurate subjective reaction rating scale for complete aircraft‐noise flyover cycles. The committee has completed the first part of a 2‐year research project that includes considerable experimental activity. This report describes the work performed to date and the plan for the remaining program. In the past, individual investigators in the field of subjective reaction to aircraft noise have developed a variety of rating methods. However, it has become increasingly clear that these have limited reliability. With the formation of the R‐6 Committee, six laboratories working in this general field have formed a cooperative organization to remedy this problem. The committee has developed a detailed research plan that will result eventually in a reliable subjective reaction rating scale for aircraft noise. In addition to this long‐range plan, the committee has assembled descriptions of each participating test facility, has retained individual and laboratory consultants, has conducted a comprehensive acoustical calibration of each laboratory, and has completed some preliminary judgment tests.

Carefully presented instructions are a basic requirement of successful psychoacoustical scaling studies. The term in the instructions which refers to a subjective experience uniquely defines the type of scale constructed. This paper describes the degree to which a psychoacoustical scale would be modified by changes in instructions. The results of 2 studies are reported. The first discusses the differences in subjects' responses to instructions based on 3 different key words—loudness, noisiness, and annoyance. The second is concerned with the effect on subjects' responses of mixed instructions (i.e., where more than one key word appears in a single set of instructions). The results indicate that different instructions “set” subjects to give different emphasis to various physical aspects of sound, and that instructions based on a combination of 2 key words yield ratings significantly different from ratings given to the same sounds when the key words are used individually. A recommendation is made that instructions be selected which set subjects to emphasize sound dimensions relevant to particular noise problems.

It is imperative to investigate the acoustical properties of roms with the aid of models prior to construction. Two sound sources have been developed to facilitate these investigations. An air jet utilizing four intersection jets provides a nondirectional random noise, over a frequency range of 2400 cps to over 100 kcps for the study of the steady‐state properties of rooms. A repeating spark generates an acoustical pulse having a rise time of less than 2 μsec and a duration of 20 μsec, providing a source for the study of the reflection of pulses within a room. These sources, with a 14‐in.‐diam microphone, are used in 1/50 scale models. Results utilizing these acoustical tools are illustrated by data on the absorption of direct sound over a sloping audience surface, reflection of sound from a canopy, side‐wall reflections, and the acoustical performance of an orchestra enclosure.