Fish Guidance Systems Limited

Sound Projector Array (SPA) Systems


SPA systems are primarily used to deflect fish from entering water intakes or water channels, but can also be used for other applications, including deflecting fish from within pumping chambers and herding fish from areas as part of fisheries management protection or exclusion measures. Typical installations include power stations, industrial facilities, drinking water, irrigation and pumping station intakes. A SPA system is analogous to a public address or domestic hi-fi system, using underwater Sound Projectors (or loudspeakers), connected to Control Equipment by cables, to create a repellent acoustic field in front of a water intake. FGS can supply different models of SPA system to suit different site conditions. Where additional deterrent is required the Sound Projectors are coupled with FGS’s High Intensity Lights to provide a SILAS system.

Sound Projector Array (SPA) acoustic fish deflection systems comprise the following components:

  • Signal Generator
  • Power Amplifiers
  • Diagnostics and Alarm Unit
  • Control Equipment Enclosure
  • Sound Projectors
  • Interconnecting Cables & Underwater Connectors
  • Deployment System

Signal Generator

FGS Signal Generators can hold up to eight signals. A single Signal Generator is used where the target fish species are migratory and or non-resident, whilst an eight Signal Generator is generally required for resident species to avoid habituation to any one signal.

Power Amplifiers

The Signal Generator feeds into a bank of audio frequency power Amplifiers that boost signal levels to the required output levels for the transducers.

Air Blower/Compressor Pipe

A temperature/pressure resistant pipe delivers air from the air blower or compressor to the BAFF control equipment.

Diagnostics and Alarm Unit

The Diagnostics Units monitor the output of the Amplifiers and condition of the Sound Projectors and send an alarm to a monitoring site if a fault is detected.

Control Equipment Enclosure

The Signal Generator, Power Amplifiers and Diagnostics and Alarm Units combine to provide the Control Equipment of a SPA system. The Control Equipment is typically housed in an air-conditioned enclosure, or an enclosure within an air-conditioned building.

Sound Projectors

Underwater Sound Projectors are used to create the underwater sound field. Generally, a linear array of Sound Projectors is used to create a field of repulsion. We refer to this array as the ‘Sound Projector Array’ or SPA. The Model 15-100 Sound Projector is primarily intended for shallow freshwater applications (

Interconnecting Cables & Underwater Connectors

Generally underwater grade cables connect each Amplifier to a series of Sound Projectors. All of the connections use underwater mateable connectors.

Deployment System

A deployment system allows the Sound Projectors to be raised and lowered for inspections and maintenance and also avoids the costs associated with using divers. Deployment systems may take many forms ranging from a simple rail to a custom made structure.

Additional Notes

The majority of systems now supplied by FGS are SILAS systems, incorporating High Intensity Lights with the acoustic signal. SILAS systems are based upon Sound Projector Arrays, but the components have been updated, and the main components are outlined in the SILAS System Description.

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