Aural discrimination of target echoes in white noise by human observers using broadband sonar pulses

Abstract

Sonar echo‐discrimination performances were measured as a function of S/N with three human observers. Targets included hollow cylinders of aluminum and glass having diameters of 3.81 and 7.62 cm, and a solid 7.62‐cm aluminum cylinder. The subjects were required to discriminate between the 7.62‐cm solid and hollow aluminum cylinders, and between the hollow aluminum and glass cylinders. Digital recordings of target echoes were obtained using dolphin‐like echolocation signals, and played back to the subjects at 150 of the original sample rate. The slope of the psychometric function for the solid‐hollow discrimination was approximately 2.2% correct/dB, and between 0.7 and 1.3% correct/dB for the hollow aluminum‐glass discrimination. The average 75% correct response threshold occurred at a S/N of 22 dB for the solid‐hollow discrimination, and at 42 dB for the 7.62‐cm hollow aluminum‐glass discrimination. The S/N for 75% detection of the 7.62‐cm hollow aluminum cylinder was 11 dB for one of the subjects, indica...