In recent years, there has been a proliferation of knowledge concerning highway noisegeneration and control. There has also been many kilometers of noise barriers constructed.Two countries that have led in the area of highway noise control are Japanand the United States. Each country has developed an accurate prediction methodology, although there are significant differences between them. One objective of this paperis to discuss these differences, as one way of introducing the United States methodinto the international literature. The other objective of the paper is to present a methoddeveloped by the authors to quantify the insertion loss degradation caused by the presenceof parallel reflective highway noise barriers. This method allows the user to locatespatially all image sources, and to determine their magnitude. Comparisons with results from scale model studies indicate that this method is quite accurate.

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Foil-shaped manganin gauges are used for pressure measurement of shock wave insolid. Some experiments of resistance change under shock pressure are made to discussthe effectiveness of their gauges as in-material gauge. The resistance changes aremeasured as a function of shock pressure. Shock waves are generated into solid bya single-stage gas gun. Shock pressure are obtained by using the impact velocity ofprojectile and the shock compression data of standard materials, such as copper, sapphireand fused quartz. The results by the foil-shaped manganin gauge used here arein good agreement with the ones under the static pressure, while the other results undershock pressure using manganin wire by other workers have been not in agreement withstatic data. It is concluded that the foil-shaped manganin gauge used here is very useful as in-material gauge for shock pressure measurement.

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A whole view on the harmonic generation in organ pipes is presented. It consists ofelementary processes:(a) excitory source spectrum generation by the jet, (b) filtrationby the inharmonic normal modes of the passive system, and (c) radiation from the pipeends. Lateral jet velocity distribution is responsible for the source spectrum. Filtrationand radiation emphasize the resultant source spectrum. Harmonic generationmechanism is classified into the unsaturated and saturatea regimes, and formulated onthe basis of current-and pressure-drive models. Theoretical consideration deduced:(1) Contribution of the pressure-drive to the harmonic generation is not significant.(2) Harmonic structure and its development in the unsaturated regime are defined bythe matrix of the jet offset and the vector of the jet deflection amplitude.(3) A decisivefactor determining the harmonic structure in the fully saturated regime is the time interval ratio of the jet switching action.

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Some experiments on the loudness of impact sound were carried out, where the modelimpact sounds based on the actual ones were used as test stimuli. From these experiments, it is clarified that the reading of the sound pressure level through a circuit witha certain time constant can well describe the loudness of impact sounds than its soundenergy does. The values of the time constant of exponential averaging circuit are investigated, accordingly. As the results of this study, a sound level meter with two exponentialaveraging circuits, one of which has5ms rise time constant and250ms decay timeconstant, and the other has125ms rise time constant and250ms decay time constant, shows a good agreement with loudness of a single or repeated impact sounds in the same way as in the loudness of steady sound.

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