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Six different acoustic pingers and signals were tested at sea to determine their impact on dolphin behavior. Two prototype devices from the Board Iascaigh Mhara (BIM) were tested. One was a continuous pinger (CP) and the second a responsive pinger (RP). These were tested on five occasions. A third modified RP was also tested on five occasions and a fourth RP was modified into a multiple signal output device and tested on 15 occasions. In addition, the CETASAVER and Dolphin Deterrent Device (DDD) were tested on five and ten occasions respectively. The BIM and RP acoustic pingers did not elicit any response from the dolphins. The CETASAVER and DDD elicited a mild response. The authors suggest significant modification to the signal type or source level. At the current state of development acoustic pingers may not provide effective deterrent signals to dolphins.