Warren C. Kennedy

Apparatus for treating flowing working gases particularly to reduce the noise in operation thereof

A device for treating flowing working gases in order to reduce their operational noises and in most instances also to increase their operating efficiency comprises a flowing working gas operating device which has a discharge conduit with at least one discharge opening for the outflow of the working gas. A check valve is associated with the discharge and includes an elastic valve member movable to close the opening when the flow thereof decreases to a predetermined amount for example as determined by the reduction of pressure of the gases so as to prevent any back flow into the conduit which is likely to produce noise. The elastic member may comprise an ordinary rubber band which is preferably held in position by a guide member so that when the pressure of the working gas is sufficient the gases will flow out of the discharge conduit and will be directed through one or more chambers so as to cause the gas to flow into a whirling vortex flow and preferably in a substantially annular path so as to order the gases and to thereby increase their efficiency of operation.

Quantitative method for evaluation of the state of piano hammer felt tonal regulation

A method for measuring dynamic hardness of elastic materials is applied particularly to determining the state of tonal quality for a piano hammer. The method includes selecting a piano hammer of predetermined type from a set of piano hammers, causing the selected piano hammer to strike against an impact surface having the form of a piano string or string grouping appropriate to a piano hammer of the predetermined type, measuring one or more elements of force and motion of the piano hammer striking the impact surface, e.g. force, determining, e.g., the cut-off frequency of the power spectrum for the selected piano hammer striking upon the impact surface, and comparing the determined cut-off frequency of the power spectrum for the selected piano hammer against a predetermined range of cut-off frequencies of power spectrum acceptable for piano hammer of the predetermined type. An apparatus for testing is also described.

Chart for estimating the efficiency of the broadband sound‐power radiation by randomly vibrating pipe walls

A general curve is derived for the broadband radiation efficiency of a pipe where walls undergo random vibration. Once the mean amplitude of vibration of the pipe wall is known one can use this curve to predict the broadband sound power level radiated by the pipe.

Simulation of Acoustic Noise Generated by an Airbreathing, Beam‐Powered Launch Vehicle

A simple acoustic model is developed for predicting the noise signature vs. power level for advanced laser‐propelled lightcraft — capable of single‐stage flights into low Earth orbit. This model predicts the noise levels generated by a pulsed detonation engine (PDE) during the initial lift‐off and acceleration phase, for two representative ‘tractor‐beam’ lightcraft designs: a 1‐place ‘Mercury’ vehicle (2.5‐m diameter, 900‐kg); and a larger 5‐place ‘Apollo’ vehicle (5‐m diameter, 5555‐kg) — both the subject of an earlier study. The use of digital techniques to simulate the expected PDE noise signature is discussed, and three examples of fly‐by noise signatures are presented. The reduction, or complete elimination of perceptible noise from such engines, can be accomplished by shifting the pulse frequency into the supra‐audible or sub‐audible range.