Underwater Sound System Research Articles

Hydroacoustic stand for evaluating underwater sound systems in a measurement pool

Measurement of sonar parameters in laboratory conditions is a powerful tool for development, control and diagnostics. The realization of such a tool requires the construction of a measuring pool and its equipment with digital channels for receiving and generating sonar signals. An essential requirement for the measuring equipment is to quantify time and amplitude signals with the necessary accuracy and speed. The paper presents a new stand for evaluating the parameters of active and passive sonar systems. The stand is based on the PXI console of National Instruments and the underwater receiving channel of Bruel & Kjaer. Software solutions for the synthesis, transmission, reception and analysis of acoustic signals with different pulse lengths and intrapulse modulations have been developed through the LabVIEW software platform. VI instruments were developed for digital processing, and visualization of signals, and the ability to measure Sonar Transducer parameters in a test tank.

New underwater sound system for synchronized swimming: The 9th International Swimming Federation Championships

There have been concerns about the differences between underwater sound fields in a temporary fiberglass-reinforced plastic (FRP) pool and in a conventional reinforced concrete (RC) pool. A temporary FRP pool was to be used for competitions at the World Swimming Championships in Fukuoka. We considered three items as key factors for a swimming pool used for synchronized swimming: (1) the sound source itself (output level, fluctuations in frequency characteristics); (2) the effect of materials used in pool construction upon sound source installation conditions; and (3) the effect of the mth mode low-frequency cutoff in ‘‘shallow water.’’ To improve basic problems related to the first factor, we developed a new actuator-driven underwater sound system (YALAS), which can eliminate the effect of installation conditions for underwater speakers in the FRP pool. This new underwater system has now seen practical use in competitions. The report summarizes this new underwater sound system and compares the system with conventional systems in terms of its acoustic characteristics. The system can offer music with sufficient audibility in water. We gained a good reputation with competitors because the system showed superior performance to conventional systems in sound volume and quality, and in uniformity of sound distribution.

The new underwater sound system for synchronized swimming: An example of The 9th FINA Swimming Championships FUKUOKA 2001

The new underwater sound system for synchronized swimming: An example of The 9th FINA Swimming Championships FUKUOKA 2001

An experimental comparison between a pulse and a frequency-modulation echo-ranging system

Experiments designed to study the operation of a jrequency-modulation echo-ranging system and compare this with a pulse system are described. The results show that a previous theoretical study by the author1 can be used as the basis of the design of a frequency-modulation system which may compare very favourably with a pulse system designed for the same purpose. When the bandwidth of the pulse system is limited, as it sometimes is in underwater sound systems, the frequency-modulation system can give much superior results. On the other hand, the pulse system can provide a much higher resolution in range if the bandwidth of the system is restricted only by that of the transducer arrays.