The Acoustic Pressure Tank Facility (APTF) of the Naval Undersea Warfare Center (NUWC) Division Newport provides acoustic testing over a wide range of simulated ocean environments. Temperatures from 2 degrees Celsius to 35 degrees Celsius and hydrostatic pressures up to 18.6 megapascals (2700 pounds per square inch), corresponding to depths up to 1860 meters, are available.

The APTF includes a large water filled tank with a three carriage positioning system, three independent rotators, and a fully automated data gathering system. The facility can provide measurements of the acoustic characteristics of sonar system components and other underwater acoustic devices and materials, including (but not limited to) transducers, hydrophones, small arrays, baffles, coating materials, and windows. It has the capability for extensive acoustic, mechanical, and electrical measurements.


The APTF contains a closed steel tank 3.81 meters in diameter and 11.1 meters in length with two access ports. The larger port is 1.85 meters in diameter, atypically large for a tank of this size. The tank is lined on one end with sound absorbing wedges to reduce reverberation and allow the use of high pulse repetition rates. The monolayer tank wall construction allows quiet pressure cycling for extraneous noise evaluation. The tank is suspended on air bags to minimize ground borne noise. An external coating on the tank provides thermal insulation.

The APTF offers a wide range of rigging options. An external rotator located above the small port (0.84 meters in diameter) can accommodate devices and/or material samples up to 1180 kilograms. An underwater rotator located below the large port (1.85 meters in diameter) allows devices and/or material samples of up to 2700 kilograms to be rigged. Two of the three carriages can accommodate devices up to 45 kilograms. The third carriage contains a motorized positioning system with full 360 degree azimuthal control and vertical control over a 202 millimeter height. The rigging weight limit of this latter carriage is 27 kilograms. Each of these carriages can be independently positioned along the axis of the tank.

Measurement Capabilities

A six channel Transducer and Hydrophone Acoustic Measurement and Evaluation System (THAMES) provides the APTF with a fully integrated, computerized, automated acoustic test setup, control, data gathering, and analysis capability. THAMES is a Windows system based on LabVIEW. THAMES integrates control and measurement software with sophisticated Hewlett Packard (HP) VXI data gathering modules and all required supporting instruments and controls.

Continuous wave, pulse, and arbitrary waveform generation are available. The system provides active and passive acoustic measurements; directivity patterns can be provided for receivers and transmitters along with accurate measurement of harmonic distortion of transmitted and received signals. APTF capabilities also include measurement of ambient noise levels and spectrum analysis of acoustic responses.

APTF measurement reports include (but are not limited to): linearity (transducer output versus input power); bearing error for multi-mode hydrophones; sum difference (null balance) magnitude and phase; and absolute reciprocity calibration. The APTF can provide measurements of capacitance and dissipation factor, direct current resistance, and insulation resistance for devices tested. The APTF can also provide echo reduction, insertion loss, and electroacoustic characteristic measurements. Digitized photographic images can be obtained using an underwater camera. Calibration data is available at the time of the measurement in hard copy and/or electronic format. Formal calibration memoranda may also be produced, upon request, which include presentation quality graphical and tabular outputs.

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For questions or assistance in obtaining measurement services,
please contact the APTF Facility Head at: