A surface explosion of 500 tons of TNT at the Suffield Experimental Station Alberta, Canada, was monitored with a solion infrasonic microphone at a horizontal distance of 299 km to the southwest. The frequency response of the infrasonic microphone extended from 0.01–50 Hz. Statistical analysis using the power spectra and deterministic analysis using the amplitude spectra show a primary signal component at 0.26 Hz. Additional examination of the autocorrelation function and the power spectra indicates that atmospheric turbulence modulated the infrasonic wave as it propagated to the monitoring site. It is also suggested that his modulation could provide a measure of the atmospheric turbulence along the propagation path.

The solion infrasonic microphone is an electrochemical pressure transducer designed for the measurement of atmospheric-pressure variations. An over-all transducer frequency response from 0.003-50 cps and a dynamic range from 0.1-1000 dyn/cm •' has been obtained with the design described. Stability, sensitivity, low power consumption, and remote-operation capability are the inherent features of this new acoustic tool. Descriptions of the solion transducer, the infrasonic microphone, and the over-all response of the system are presented. INTRODUCTION HE detection of infrasonic pressure waves in theatmosphere presents unique problems in instrumentation. The difficulties are increased when broadband data are to be investigated at relatively lowpressure signal levels. The selection of a suitable transducer for operation at both low frequencies and low-pressure levels has posed problems of both stability and sensitivity.The solion full-wave linear pressure detector is an electrochemical transducer that has satisfactorily demonstrated the ability to detect low-frequency, low-pressure, acoustic signals. A description of the infrasonic microphone is presented and includes response curves for the microphone and associated electronics. I. SOLION PRESSURE TRANSDUCERThe solion I is a low-power-consumption electrochemical device, commonly known as a redox system. In a redox system, the electrochemical reactions are completely reversible, and the electrode system does not enter into the reaction, except to remove or inject electrons. The redox system consists of an electrode set immersed in a solution containing soluble forms of the same chemical in two different oxidation states. For the solion transducer, this solution is generally an iodine/ iodide-water electrolyte system. The name solion is derived from the phrase "ions in 1 j. L. Collins

C1. RCA Victor "Dynagroove" System. HARRY F. OLSON, gC•zl Laboratories, Princeton, New Jersey.raThe RCA Victor "DYN^GRO0VE" system is a planned evolution of improvements in all aspects and elements of sound recording by means of disk records. The main objective has been to provide a distinct improvement in performance by the development of a new cohesive and integrated system from the artist's conception of the music to the reproduction of the sound as perceived by the listener. Jersey.--Condenser microphones using electret foil are discussed in this paper. Frequency response, sensitivity, and distortion of these systems have been described previously. During the past year, the stability of electret microphones has been measured. Over this period, the sensitivity has not changed more than -+1.5 dB. An independent study of the surface charge of electret foils has been conducted in order to better understand the mechanism of

The pressure variations of the atmosphere at White Sands Missile Range, New Mexico, were recorded, using a solion infrasoniC microphone array. The dimensions of the square array were 10 000 ft per side. The solion infrasonic microphone monitored data in the pressure range of 0.1–500 dyn/cm2 and in the frequency region of 0.033–50 cps. Measurements were made during high winds (20–30 kt) and very low winds (0–2 kt). The statistical nature of the infrasonic atmospheric-pressure data obtained is presented by the use of probability density functions, autocorrelation functions, crosscorrelation functions, power spectra, and crosspower spectra. [This work sponsored by the U. S. Army Electronics Research and Development Activity, White Sands Missile Range, N. M., under contract DA 36-039 SC-90719.]

An infrasonic generator utilizing a single bellows driven by a linear displacement transducer has been constructed. The generator has a dynamic range that extends from 0.5 dyn/cm9 to 600 dyn/cm2 and a frequency response of +0.5 dB, −0.6 dB from 0.001 Hz to 10 Hz. The infrasound generated by this device will be utilized for the study of the effects of infrasound on human beings. [This research is supported by National Science Foundation Grant 6K 1588].