What negatively affects sound propagation in water when using an Hydroacoustic Position Reference (HPR) system?

Using a Hydroacoustic Position Reference (HPR) system relies on sound waves traveling through water to determine position. Thruster noise can significantly interfere with the clarity of these sound signals. When thrusters operate, they create vibrations and turbulence in the water which generate additional sound waves. These extraneous noises can mask the acoustic signals sent and received by the HPR system, leading to reduced accuracy and potential position errors.

Wind turbulence, water temperature variations, and subsurface currents can affect sound propagation, but they generally do not produce noise in the same way that thruster operations do. Wind can create surface waves, impacting the acoustic signals indirectly, while temperature variations can influence the speed of sound in water, and subsurface currents might alter the path of sound waves. However, these effects tend to be more consistent and predictable than the disruptive nature of thruster noise, which can lead to immediate and unpredictable interference with the HPR functionality. Thus, thruster noise poses a direct and significant challenge to the accuracy and effectiveness of acoustic positioning systems.