摘要:

Using a reverberant chamber, it is possible to radiate a partially coherent ultrasonic beam into a free field. This type of acoustic secondary source is shown to be analogous to the Lambertian source in optics. The features and potential uses of this type of field are in marked contrast to the case of fully coherent ultrasonic radiation produced by plane or focussed transducers. The partially coherent secondary sources are not difficult to construct in a laboratory setting, and provide a useful alternative in ultrasonic measurements of materials properties, and other applications such as imaging.

ISSN:0001-4966    

DOI:10.1121/1.391063

出版商:Acoustical Society of America    

年代:1984

数据来源: AIP

摘要:

A backward masking function relating target detection to masker delay was generated for a bottlenosed dolphin in an active echolocation target detection task. The masker was triggered by each outgoing echolocation click and could be temporally adjusted from coincidence with the target echo to delays of 700 μs. The animal reported target condition using a go/no‐go response procedure. A modified method of constants was used to present the four masking delay intervals. Results indicated that 700‐ and 500‐μs delays had little effect on target detection. However, as the delay was reduced to 100 μs, detection dropped to chance performance. The calculated 70% detection threshold corresponded to a delay of 265 μs. The results are discussed in support of the view that time separation pitch (TSP) may be an analytic mechanism used by the dolphin to discern various within‐echo target attributes rather than an analytic mechanism for determining target range.

ISSN:0001-4966    

DOI:10.1121/1.391016

出版商:Acoustical Society of America    

年代:1984

数据来源: AIP

摘要:

Difference limens for auditory distance discrimination were determined using the method of limits. Eight untrained subjects were tested across a wide range of distances (49 to 4876 cm) using broadband noise sources. For sources in excess of 304 cm, the Weber ratios observed approximated the function predicted by the inverse first power loss equation. At the longer distances, the subjects appear to be judging distance on the basis of the loudness difference cue. At the shorter distances (49 to 304 cm), the Weber ratios were considerably larger than would be predicted from the inverse first power loss equation. In this range, distance discrimination becomes increasingly degraded as the referent source approaches the subject.

ISSN:0001-4966    

DOI:10.1121/1.391064

出版商:Acoustical Society of America    

年代:1984

数据来源: AIP

摘要:

Underwater sounds we have measured are interpreted to have been produced by lightning strikes to water in the Gulf of Mexico. The range to the storm cells was approximately 30–40 km. Measurements with a hydrophone tethered to the research vessel TommyMunroallows us to estimate the total acoustic energy in the sound field. Our estimates are compatible with what one might expect on the basis of the total electrostatic energy dissipated by a typical flash to the ground.

ISSN:0001-4966    

DOI:10.1121/1.391065

出版商:Acoustical Society of America    

年代:1984

数据来源: AIP

ISSN:0001-4966    

DOI:10.1121/1.391066

出版商:Acoustical Society of America    

年代:1984

数据来源: AIP

ISSN:0001-4966    

DOI:10.1121/1.391072

出版商:Acoustical Society of America    

年代:1984

数据来源: AIP

ISSN:0001-4966    

DOI:10.1121/1.391077

出版商:Acoustical Society of America    

年代:1984

数据来源: AIP

ISSN:0001-4966    

DOI:10.1121/1.391078

出版商:Acoustical Society of America    

年代:1984

数据来源: AIP

ISSN:0001-4966    

DOI:10.1121/1.391081

出版商:Acoustical Society of America    

年代:1984

数据来源: AIP

ISSN:0001-4966    

DOI:10.1121/1.391088

出版商:Acoustical Society of America    

年代:1984

数据来源: AIP