Reverberation chambers used for acoustical measurements should have completely random sound fields. We denote by R the cross-correlation coefficient for the sound pressures at two points a distance r apart. R = 〈p1p2〉Av/(〈p12〉Av〈p22〉Av)12, where p1 is the sound pressure at one point, p2 that at the other, and the angular brackets denote long time averages. In a random sound field, R = (sinkr)/kr, where k = 2π/(the wavelength of the sound). An instrument for measuring and recording R as a function of time is described. A feature of this instrument is the use of a recorder's servomechanism to measure the ratio of two dc voltages. The results of correlation measurements in reverberant sound fields are given.

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This publication is a guide offering practical solutions for the ordinary noise problems that a person is likely to meet in his home, while traveling and at work. The discussion describes the ways in which sounds are generated, travel to the listener, and affect his hearing and well being.Recommendations are given for controlling noise at the source and along its path of travel, and for protecting the listener. The guide instructs the reader by way of "Warning signs" on ways and means of determining whether prolonged exposure to a noisy environment may be hazardous to his hearing. General principles for selecting quiet appliances are given. The remedies for noise problems deal both with prevention and with selection of quiet alternatives to existing noise sources.Ways of searching for the sources of noise and the paths over which they travel to the listener are described. A detailed index is given for individual noise sources and the solutions to the problems they present.General ways of looking for inherently quiet homes ajid travel accommodations are described.In a final chapter, there are suggestions for enlisting commvinity help where large external sources of noise must be quieted, such as those arising from public tremsportation and public utilities .

The reverberation chamber technique was used to determine the sound spectra and acoustic power radiated by air jets over a range of subsonic velocities. Different air jets were used with round and square velocity profiles; nozzles of circular cross section, and nozzles with saw-tooth and corrugated ends were also used. Of these nozzles only the latter type gave a significant (9 db) reduction in sound power output for a given exit-pressure ratio. A study was made of the limitations of the reverberation chamber technique caused by the absorption in the chamber. When this absorption became considerable, the measurement of sound pressure level in a circle around the sound source revealed a directional pattern, and the assumption of uniform energy distribution in the chamber became invalid. This situation was noticeable at frequencies above 5 kc in the National Bureau of Standards chamber, owing to air absorption.

The data obtained at the National Bureau of Standards on the sound insulating properties of building structures are summarized. The results of the two previous Supplements to BMS Report 144 (1955) are included, together with later results obtained through January 1964. Single figure ratings, STC and INR, for airborne sound transmission and impact sound transmission, respectively, as well as the octave frequency band spectra of impact noise, are included as additional information. A brief description of the sound-measuring techniques is given.