| 摘要 |
A chamber comprising a base and cap configured to contain a liquid under pressure, an aperture is provided in the cap through which a hydrophone (figure 1: 5) is exposed to the liquid, a reference sensor 10 is provided in the chamber and a transducer to apply an acoustic pressure to the liquid. The transducer may be a piston 8 and it may generate waves over a plurality of frequencies. A valve may be provided to decouple to reference sensor 10 or the piston 8 from the rest of the chamber, the valve may be a slide valve. The temperature of the chamber may be determined and a thermal bath may be coupled to the pressure chamber. The piston controller may be configured to measure the temperature difference between the thermal bath and the chamber and only actuate the piston 8 when the difference is below a predetermined limit. The liquid in the chamber may be degassed. The calibration may take place at acoustic frequencies as low as 0.001 Hz and at hydrostatic pressures of at least 5000 psi. A method claim is also included for calibrating a hydrophone over a plurality of frequencies. |
