Listen to a sonar ping example.

Development of Navy sonar received a major impetus in 1912 because of the Titanic sinking.   In the quest for ever-greater range, navies pushed the engineering analysis and the technology of solid electro-mechanical transducing materials from quartz through nickel to lead-zirconate-titanate (PZT) to the terbium alloy.   The sonar ping is included here as a light-hearted way to acknowledge the indebtedness of the next generation of state-of-the-art emissions-abating diesel fuel injectors to Navy sonar.