Observation of low-frequency wave generation in a bubble layer. (1996)

The difference-frequency sound generation as a result of the interaction of two high-frequency harmonic waves in a bubble layer in water are investigated experimentally and theoretically. As it was shown before, the use of the layer resonance can increase the efficiency of the nonlinear transformation of the signal. Here the data of the experiment with a bubble layer of the thickness of about 10 cm in the anechoic tank are presented. One of the incident (primary) wave frequencies was 60 kHz while the another varied from 59 to 50 kHz, thus providing the low-frequency signal in the range of 1 to 10 kHz. Due to the first-mode layer resonance, this secondary signal had a pronounced maximum at the frequency of 2.2 kHz (while the primary wave was in resonance with the bubbles of the radius about 45 μm, and no resonance in the layer was observed for it). The bubble volume ratio from these experiments was estimated to be about 1.4×10−4. A theory was also developed for this type of interaction which described well the experimental results. [Work was supported by the Russian Foundation of Fundamental Research Grant No. N0-93-05-8074 and by the Science Opportunity Program of the Office of Naval Research.] Standards Committee S3 on Bioacoustics. The current status of standards under preparation will be discussed. In addition to those topics of interest, including hearing conservation, noise, dosimeters, hearing aids, etc., consideration will be given to new standards which might be needed over the next few years. Open discussion of committee reports is encouraged. The international activities in ISO/TC 43 Acoustics, and IEC/TC 29 Electroacoustics, and ISO/TC 108/SC4 Human Exposure to Mechanical Vibration and Shock, will also be discussed. The Chairs of the U. S. Technical Advisory Groups for ISO/TC 43 (P.D. Schomer), IEC/TC 29 (V. Nedzelnitsky), and ISO/TC 108/SC4 (H. E. von Gierke) will report on current activities of these international Technical Committees and Subcommittees, including the meetings of ISO/TC 43 and IEC/TC 29 held in Pretoria, South Africa, in February 1996. Scope of S3. Standards, specifications, methods of measurement and test, and terminology in the fields of mechanical shock and physiological acoustics, including aspects of general acoustics, shock, and vibration which pertain to biological safety, tolerance, and comfort. Standards Committee S1 on Acoustics. Working group chairs will report on their preparation of standards on methods of measurement and testing, and terminology, in physical acoustics, electroacoustics, sonics, ultrasonics, and underwater sound. Work in progress includes measurement of noise sources, noise dosimeters, integrating sound-level meters, and revision and extension of sound level meter specifications. Open discussion of committee reports is encouraged. The international activities in ISO/TC 43 Acoustics, and IEC/TC 29 Electroacoustics, will also be discussed. The chairs of the respective U. S. Technical Advisory Groups for ISO/TC 43 (P.D. Schomer) and IEC/TC 29 (V. Nedzelnitsky) will report on current activities of these international Technical Committees, including the meetings of ISO/TC 43 and IEC/TC 29 held in Pretoria, South Africa, in February 1996. Scope of S1. Standards, specifications, methods of measurement, and test and terminology in the field of physical acoustics including architectural acoustics, electroacoustics, sonics and ultrasonics, and underwater sound, but excluding those aspects which pertain to biological safety, tolerance and comfort.