Abstract: An electroacoustic transducer comprising an electromechanical transducer and a vibratory component. The latter has a generally cylindrical side wall, an outwardly directed portion at the base of the side wall, and a generally planar vibratory top wall extending inwardly from the rim of the side wall further from its base to close the upper end of the cylindrical side wall. The said outwardly directed portion is mounted on the electromechanical transducer.

Abstract: Apparatus for measuring the time taken for sound to travel a predetermined distance, including a transmitter electroacoustic transducer for transmitting an acoustic signal, and a receiver electroacoustic transducer, spaced from the transmitter electroacoustic transducer, for receiving the transmitted acoustic signal. The apparatus has a sound reflective surface spaced from the receiver electroacoustic transducer, so the latter also receives a reflection of the acoustic signal, and timing electrical circuitry connected to the receiver electroacoustic transducer to provide a measure of the time delay between the respective receptions by the receiver electroacoustic transducer of the acoustic signal and its reflection. The invention extends to a flowmeter (10) which incorporates such apparatus and an anemometer which incorporates such apparatus. The apparatus can be adapted to measure the speed of sound. The invention extends to the corresponding methods which make use of such apparatus.

Abstract: An electroacoustic transducer An electroacoustic transducer comprising an electromechanical transducer and a vibratory component. The latter has a generally cylindrical side wall, an outwardly directed portion at the base of the side wall, and a generally planar vibratory top wall extending inwardly from the rim of the side wall further from its base to close the upper end of the cylindrical side wall. The said outwardly directed portion is mounted on the electromechanical transducer.

Abstract: In a nuclear reactor installation comprising a fluid-cooled nuclear heat source within a primary pressure vessel, this latter and also auxiliary facilities including new and spent fuel stores are enveloped together within an outer envelope which is designed to afford protection from external missiles; but within this envelope the auxiliary facilities are isolated from the primary pressure vessel by pressure tight structure which, with the major part of the outer envelope, constitutes secondary containment means of the installation.

Abstract: A prestressed concrete container having a chamber therein and a removable concrete member closing the chamber and held in its chamber-closing position by primary and secondary hold-down means each comprising members held fast with the concrete of the container and with the secondary hold-down members passing through the concrete of the closure member.