TECHNICAL NOTES AND RESEARCH BRIEFS

region, as well as by type and size of residence area. Findings in this report are compared with those from several previous hearing surveys in this country, and appendices provide technical infor- mation on survey methodology and defi- nitions of demographic terms used. Copies of the report may be purchased for 30 cents from the Superintendent of Docu- ments, U. S. Government Printing Office, Washington, D.C. 20402.•-•

"Ultrasonic Recording Scanner Used for Nondestructive Weld Inspection," NASA Tech. Brief 66-10220. The scanner em-

ploys two point-beam ultrasonic trans-

ducers mounted in a V configuration, so that the beams intersect at a common

point on the test surface. The test results are displayed on a conventional paper chart recorder.

In operation, the transducers are oscil- lated back and forth across the weld

area. As long as the weld area presents a uniform field to the transmitted ultra-

sonic beam, a trace is recorded on the chart. The moment a change appears in the weld area, the changing ultrasonic signal energizes a solenoid, causing the stylus to retract from the paper, leaving a blank space. The resultant chart pro- vides a simple, direct-reading record of

the weld quality, without requiring further processing of the data.--•

"Multicolor Stroboscope Pinpoints Reso- nances in Vibrating Components," NASA Tech. Brief 66-10223. This report dis- closes a visual detection system using three different colored lights, that will rapidly scan a vibrating multicomponent assembly and provide a visual indication of resonant components.•

NASA Tech Briefs are available for 15

cents each from the Clearinghouse for Federal Scientific and Technical Infor-

mation, Springfield, Va. 22151.•-•

15.1

LAGNIAPPE

THOSE MYSTERIOUS AND DISCONCERTING

popping and cracking sounds that emanate from the heating system may be relieved by a new process for assembly of baseboard heating units. The conventional mechanical method of assembling the fins and side sheets of baseboard heaters does not allow

the fins to move, so that cracking and pop- ping results when the fins expand during the heating cycle. Now a rubber-based commercial adhesive is being used by Twin Temp Corp., in the assembly of baseboard heating units to eliminate noise and metal fatigue problems, while at the same time

reducing manufacturing costs. The ad- hesive absorbs the stresses created in the

fins during expansion.--•

A SYSTEM FOR REMOTE READING O•F WATER

and gas meters by acoustical means is pro- posed in Patent 3,313,160 granted to David A. Goldman, who says his system will permit meters to be read at rates of more than 1000 per hour without access to the dwellings. In the case of water, a mobile unit could park at a hydrant and read a large number of meters in the neighbor- hood. Each meter box is to hold a small re-

ceiver and transmitter. The central station

queries a meter by sending its individual

coded sonic pulse through the water or gas. The home transmitter then reports the reading to the central station by vibrations. (Avoid tapping on the pipes, it may cost you raoney.) •

WE NOTE Ta^T UnTRASO•IC DISHWASHrNG

equipment on a large scale is being built by Acoustica for a Los Angeles hotel. There has been some talk also about the possi- bility that home dishwashing may sometime be done ultrasonically. If that comes to pass, a word of caution seems in order: don't use the same frequency as the ultra- sonic whistles that call the neighbor's dogs to dinner!

388 Volume 43 Number 2 1968

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