Sound Power Spectrum

A sound-power spectrum for chemical rockets is given in figure 5, with data from references 15 to 18, 20, and 24. The data are primarily from undeflected rocket exhausts but include data from aerodynamically smooth bucket deflectors, which were seen in figure 4 to have efficiencies similar to those of the undeflected exhausts. The normalizing parameter, Ue dg in the quantity W(f)Ue WQ de, adjusts the measured relative sound power per Hz W(f) WQA to relative power per unit Strouhal number so...

Rocket Exhaust Noise Generation

The characteristics of rocket noise may be summarized in the following manner. The acoustic (sound) power generated by a supersonic rocket exhaust is directly proportional to the cube of the exhaust velocity. The spectrum of the noise generated is broadband in nature no discrete frequency sound is normally observed, and the spectrum peak frequency is inversely proportional to the size of the engine. Noise is radiated in all directions, but the maximum radiation is at an acute angle to the...

Definitions Of Acoustical Terminology

Acoustic Loading Acoustic loading is the spatially- and frequency-dependent sound-pressure fluctuations on the vehicle surface. Decibel p. 13, ref. 47 The decibel is a unit of level when the base of the logarithm is the tenth root of ten, and the quantities concerned are proportional to power. Note 1 Examples of quantities that qualify are power any form , sound-pressure squared, particle-velocity squared, sound intensity, sound-energy density, voltage squared. Thus the decibel is a unit of...

Overall Sound Power and Acoustic Efficiency

The overall sound-power level for undeflected rocket exhausts is summarized in figure 3, which presents data from references 15 to 23. The data include both solid-and liquid-fueled chemical rockets in the thrust range of 1.56 to 31 100 kN 350 to 7 000 000 lb , together with a few examples of clustered nozzles and nuclear-powered hydrogen supersonic jets. The acoustic efficiency, defined as the ratio of the sound ' Closed symbols single nozzles Figure 3. - Overall sound-power level for solid-...

Introduction

A space vehicle is subjected to a severe fluctuating external-pressure loading when its rocket-propulsion system is operated in the atmosphere. Such acoustic loading is described in terms of its overall sound-pressure level and its frequency spectrum and spatial correlation as functions of position over the vehicle's surface. The acoustic loading results from the broad frequency-spectrum acoustic field generated by the mixing of the rocket-engine exhaust stream with the ambient atmosphere....

References

Structural Vibration Prediction. NASA Space Vehicle Design Criteria Structures , NASA SP-8050, 1970. 2. Anon. Buffeting During Atmospheric Ascent. NASA Space Vehicle Design Criteria Structures , NASA SP-8001, revised 1970. 3. Lighthill, M. J. On Sound Generated Aerodynamically, I, General Theory. Proc. Roy. Soc. London , A211, 1952, pp. 564-587. 4. Lighthill, M. J. On Sound Generated Aerodynamically, II, Turbulence As a Source of Sound. Proc. Roy. Soc. London , A222, 1954, pp. 1-32. 5....