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Lead for Noise Control

A variety of forms of lead and leaded materials for controlling noise and vibration is available today. These forms are classified by type and use, and the theory of their performance is examined cursorily in this paper. To describe the application of these materials for acoustic purposes, five examples are given to show their effectiveness in reducing sound levels.

Electrical Discharge Machining in Production

Republic Aviation Corp. had a manufacturing problem with drilling the speed brake door of the F-105 airplane. The door is composed of annealed and heat treated Rene 41, Inconel X and titanium. To overcome this problem, electrical discharge machining was utilized to produce required holes, resulting in significant cost savings over traditional methods.

Injury in Non-Fatal Accidents *

The research paper presented here is the result of an investigation by a medical-engineering team. The study applies techniques of experimental automobile-collision injury analysis to human injuries resulting from accidental collisions. The accident characteristics, observed injury patterns, and human kinematics are presented and analyzed. The study emphasizes injuries sustained from windshield glass. Present glass characteristics are discussed and suggestions based on the cases presented are made regarding future glass technology.

Aerodynamic Wind Throb in Passenger Cars

Most automobiles, at certain speeds with at least one window open, develop a pulsating pressure which is felt mainly through the ears and is objectionable to the occupants. While this ?쏿erodynamic wind throb??is noticeable over a range of speeds, there is a fairly pronounced peak in the effect at one speed. This problem is studied analytically and experimentally. It is established that the car is a dynamic system consisting of a Helmholtz resonator excited by an edge tone. It is shown that the trouble can be corrected by changing the natural frequency, minimizing or eliminating the excitation, or increasing damping of the system.

The WHY and HOW of THE RUBBER-TIRED RAILROAD-COACH

Railroads are facing a crisis in operating costs, the urge toward reduction of unnecessary weight has become widespread and the crusade for noise abatement is no longer to be denied, according to the author. The pneumatic-tired railroad-coach not only answers these requirements, he says, but anticipates a demand for a new traveling comfort. The desire to rubberize railroad equipment is old but much fruitless research has resulted from directing it chiefly toward solid-rubber or cushion tires. Road and rail surfaces present entirely different problems so far as the tire is concerned. No uniformity of conditions obtains on highways but rails are even and smooth. A badly aligned joint such as would wreck a metal wheel makes no impression on a pneumatic tire. As simple as the tire problem may seem, its solution represents years of courageous and skillful research on the part of the Michelin company in France. Out of this has been evolved a rail-car tire which has a life comparable with that of tires in highway service and therefore is commercially acceptable. Facts from tire-performance data are stated and it is shown that light coach weight is the major need. The Budd-Michelin rail-coach is described and also the Reading-65 rail-coach. Weight comparisons are made and rail-coach body-design is discussed, as well as cost of weight.

The Place of Sound Measurements in Automotive-Noise Reduction

THE desirability of measuring sound by soundmeter, rather than by listening with human ears, is expressed by the author, who states that soundmeter measurements indicate definitely just what components of noises must be reduced and also just what has been accomplished by any given change. Usually, they may be taken so as to indicate the part responsible for the noise, and even the nature of the defect. He then considers some fundamental characteristics of human ears and of various sounds. The apparent inconsistencies of the mass of data obtained from soundmeter measurements made in connection with practical noise-problems are explained, and the physical problem of what soundmeters measure is presented, together with a discussion of the subject of sound pressure and the use of the decibel scale of sound measurement which includes definitions of the various terms and units employed. The psychological problem, that is, the interpretation of sound measurements in terms of ear sensations, is presented at length and followed by a summary. The practical problem, that is, the technique of noise reduction, is analyzed also, quieting methods are suggested under seven specific headings, and it is stated as a conclusion that sound measurements obtained with measuring instruments are an indispensable aid in achieving logical noise-reduction.