Recent sio_ucdwr items

UC Division of War Research: Bibliography of Publications

Tue, 24 Oct 2023 00:00:00 +0000

This "Bibliography of Publications" includes general background information on UCDWR, followed by the Completion Report Covering Operations of the University of California Division of War Research at the U.S. Navy Electronics Laboratory. Under Contract Nobs-2074 from 26 April 1941 to 30 June 1946, n.d.

Underwater Noise and the Distribution of Snapping Shrimp with Special Reference to the Asiatic and the Southwest and Central Pacific Areas

Thu, 13 Dec 2012 00:00:00 +0000

UCDWR No. U146. A relationship has been established between crackling ambientnoise a~d the habits and distribution of snapping shrimp* in Americanwaters, and unusually high noise levels at the higher frequencies canbe expected in the areas where these animals are known to .live. There- ·fore, it is considered important to know their geographic distributionin the inaccessible areas of the Pacific ln order that the generalsound conditions in coastal waters and areas of shoal water can beantlcipated as an aid in the use of Sonar cqutpm.ent.These an~~s live under rocks and shells on the bottom, or incoral. Evon when bottoo. condi tiona are favorable, they do not oftenlive at depths greater than 30 fathons. The report covers a survey or ·all biological literature dealing with the distribution of the noiseproducinggenera Crangon (Alphous) and Synalpheus of the Pacific Ocean,the east and west coasts of North .America and sone contiguous areas.Three charts are presented giving the geographic...

A Survey of Biological Underwater Noises Off the Coast of California and in Upper Puget Sound

Thu, 13 Dec 2012 00:00:00 +0000

UCDWR No. U100. This investigation was undertaken to obtain information onthe northward extension of crackling underwater noises characteristicof the coastal waters of Southern California and for the purpose ofobserving if there were any seasonal changes in background noises inthe Puget Sound area which had been visited previously in November1942. The regions visited include Santa Barbar.a, San Luis Obispo,Monterey and Eureka to Crescent City in California, and AdmiraltyInlet and the San Juan Archipelago in Puget Sound.The characteristic crackling noises produced by snappingshrimps were found only at Santa Barbara, San Luis Obispo, andMonterey. In the northern California and Puget Sound areas wherethese animals have not been reported the waters were relatively freefrom biological noises, only very weak crackling and piping soundswere detected. There was no noticeable seasonal change .in noiseconditions in the Puget Sound area.

The Discrimination Of Transducers Against Reverberations

Fri, 25 Apr 2008 00:00:00 +0000

The directivity index which is currently used for characterizing the directional properties of transducers, refers primarily to their ability to radiate sound power. When transducers are used in echo ranging, the directivity index is, theoretically at least, of minor interest. Of greater interest is the ability of the transducer to discriminate between the echo from a target at which it is pointed, and the reverberation returned to it from this and other directions. This discrimination is measured by other quantities, called reverberation indices. One of these concerns volume, the other surface or bottom reverberation. The purpose of the present work was to study the relations between the three indices.

Conclusions drawn from a study of typical projector patterns are as follows:

1. The volume reverberation index and the surface reverberation index of a projector are linearly related to the directivity index, provided that the directivity pattern is reasonably similar...

Underwater noise caused by snapping shrimp

Wed, 29 Jun 2005 00:00:00 +0000

Crangon (Alpheus) and Synalpheus are the two principal genera of noise-producing shrimp. These animals (not to be confused with commercial shrimp, which are noiseless) are about 3/4 inch to 1-1/2 inches long. They have one enlarged claw which produces a vigorous snap when closed. Over a large colony there is a continuous succession of snaps which causes an intense crackling noise resembling the burning of dry twigs. With increasing distance from the shrimp bed, the crackle merges into a sizzle or a hiss.