Machinery Noise Research Articles

Machinery noise considerations at the design stage

Noise legislation in industry is forcing machinery designers to consider more carefully the noise emission from their machines. It is explained how consideration of the physics of noise sources at the drawing board stage can produce quieter machinery

Acceptability and perceived quality: a study of machinery noise components using psychophysical methods

This paper presents the results of a study of listener response to sewing machine sounds. The study was designed to aid noise control engineers in the development of criteria and design strategies for the reduction of machinery noise levels and the improvement of the quality of the sound. A panel of listeners rated recorded sewing machine sounds. The stimuli were comprised of composite sewing machine sounds including varied amounts of the sounds produced by individual impacting mechanical sewing machine components. The Acceptability of the sounds and the perceived quality of the machines producing these sounds were judged by the panel trained in use of magnitude estimation, a psychophysical scaling tool. An examination of the listener response data identified problem components and shows the amounts that their sound levels would have to be changed in order to have an effect on consumer judgements of quality and acceptability.

Diagnostically oriented measures of vibroacoustical processes

In diagnostic applications of machinery vibration or noise data it is convenient to describe the whole process by a set of numbers called discriminants. Five discriminants can be constructed and measured for every vibroacoustical process. Two of them have dimensional natures and give information about process amplitude and frequency. Two others, dimensionless, give information about the amplitude and spectral spread of the process. The last one, also dimensionless, characterizes the time fluctuations of the process, and can be used to detect instability of a running machine. Numerical and experimental examples are presented.

Vibration and noise relationships: Some simple rules for the machinery design engineer

In a world in which the expert is king, countries become very small and communication between them becomes very difficult. This is so in the world of acoustics; symposia are divided into specialist sections, and experts only want to hear from greater experts than themselves. Unfortunately new technologies develop across such separations, and from time to time it is necessary to try to bridge the gaps in a manner which is simple enough to persuade each group to interest itself more widely. Such a technology is that of trying to design industrial machinery which, while increasing productivity, reduces its noise and minimizes deafness. Machinery noise emanates from heavy impacts between parts. The vibration which results from this is the flow of vibration into parts that can radiate efficiently; the noise radiated depends upon the magnitude and the wave form of this vibration, upon its frequency and upon the balance between the rate of radiation and the rate of absorption in the machine. The seriousness of the noise, and the methods of reduction must depend upon the form of the units by which it is measured. This paper goes back to first principles in trying to provide the basic physical insights which will permit an approach to machinery noise which can both be used by the design engineer looking for simple design rules, while also tempting the expert acoustician, vibration engineer and psychoacoustician to extend his interests into what must surely become a new branch of acoustic technology.

Industrial and machinery noise

Industrial and machinery noise

Vibration and noise prediction of internal combustion engine based on cascade modeling of components

In most machinery noise and vibration problems, a model of the machine as a cascade of subsystems excited by the noise (vibration) source(s) may be used in predicting the effect of any modification in the source(s) or vibration transmission paths. In this study, an acoustic-dynamic model of an internal combustion engine is developed. The excitation sources considered were combustion forces and piston slap. For combustion forces, two transmission paths from each cylinder to the engine block were considered; a path through the piston, crank shaft and bearings [R. DeJong, 1976] and another path through the cylinder head. The piston slap was assumed to be transferred to the block through the cylinder wall and upper deck of the cylinder block [T. Oguchi, 1979]. The combustion forces of each cylinder were determined from the engine design and its operating conditions. The piston slap excitation was estimated on the basis of the shape and size of the piston and cylinder and assumed to occur after the combustion. The block vibration and the radiated sound power spectrum of a four cylinder in-line diesel engine were predicted and measured under different operating conditions. The predicted and measured results agreed well above 400 Hz.

An Approach to Controling Noise of Production Machinery Developed from Noise Control of Products

An Approach to Controling Noise of Production Machinery Developed from Noise Control of Products

Prediction of machinery noise radiation using the CHIEF algorithm

This paper describes the application of the Combined Helmholtz Integral Equation Formulation [H. A. Schenck, J. Acoust. Soc. Am. 44, 41–58 (1968)] to the prediction of noise radiated from machinery with relatively smooth casings under steady running conditions. The CHIEF algorithm requires that the surface vibration distribution be specified as input. Several test cases, involving a rectangular parallelepiped resting on a rigid surface, are discussed. An experimental test is described in which a fluid-filled boxlike structure with pure-tone excitation was used. The comparison between sound pressure levels measured far from the structure and those computed from measured surface accelerations is very good.

Strategies for reducing error in machinery noise measurement

Error considerations play a significant role in the design of measurement procedures and the performance of acoustic measurements. The types of measurements performed can be broadly classified into sound field evaluations. The types of measurements performed can be broadly classified into sound field evaluations (i.e., to evaluate personnel exposure) and source characterization (i.e., to quantify source emission). The latter will be the subject of this talk. All source characterizations can be interpreted as powerlike measurements, which forms a basis for further analysis. The errors in powerlike measurements can be further categorized as methodological and site determined. The methodological errors are those differences from “truth” which result (on the conceptual level) from an ideal measurement, applying a particular test method to the ensemble of sources for which it is intended. The site-determined errors are those variations in the test results which can occur when a particular method is applied to the ensemble of possible test sites meeting the requirements of a given method. Sources of error in lab and field measurements are reviewed and evaluated in the perspective of this classification. Implications for the test engineer and standards designer are drawn.

Core Noise Measurements on a YF-102 Turbofan Engine

Core noise from a YF-102 high bypass ratio turbofan engine was investigated through the use of simultaneous measurements of internal fluctuating pressures and far field noise. Acoustic waveguide probes, located in the engine at the compressor exit, in the combustor, at the turbine exit, and in the core nozzle, were employed to measure internal fluctuating pressures. Spectra showed that the internal signals were free of tones, except at high frequency where machinery noise was present. Data obtained over a wide range of engine conditions suggest that below 60% of maximum fan speed the low frequency core noise contributes significantly to the far field noise.

Noise exposure and control on fixed marine structures

Machinery noise sources on drilling and producing platforms include engines, turbines, gears, generators, pumps, and compressors. Noise transmission is both structure borne and airborne. Exposure evaluation requires consideration of work shifts ranging up to 12 hours per day, seven days in a row, as contrasted to the typical on-shore 40-hour work week. Exposure time is not limited to the work shift for those who must live on the structure. The design problem is to avoid or eliminate excessive noise levels. If this is not feasible, noise levels are minimized both as to intensity and the physical area affected by use of quiet machinery. Enclosure and/or other acoustical treatment is then used to bring exposure within acceptable limits. Off-duty areas and crew quarters are placed in the quietest available location, and isolated from structure-borne and airborne noise. Examples of noise sources and control measures are illustrated by case histories.

CONSIDERATIONS FOR AIRBORNE NOISE CONTROL IN SURFACE SHIPS

ABSTRACTThis paper familiarizes the reader with the basic concepts of airborne noise control and demonstrates their application during ship design and construction to produce airborne noise acceptable ships. The limitations of bulkhead treatments are demonstrated to emphasize the necessity of quieting shipboard machinery if the OSHA/BUMED deafness avoidance criteria are to be achieved in machinery spaces. Two current programs to backfit machinery noise treatments into modern combatant U.S. Navy ships are discussed. The expected results are presented to support the contention that shipboard machinery spaces can be quieted, at reasonable cost, to within the OSHA/BUMED limits.

Book Reviews : REDUCTION OF MACHINERY NOISE Edited by M. J. Crocker Purdue Univ., West Lafayette, Inc. (1974)

Book Reviews : REDUCTION OF MACHINERY NOISE Edited by M. J. Crocker Purdue Univ., West Lafayette, Inc. (1974)

Method for computing sonar response to aft bearing noise sources

The search sonar on some ships has a cylindrical array shielded from its own ship's noise by a baffle. The sound-pressure levels on the cylindrical surface due to machinery and propeller noise cannot be computed by methods presented in the literature. An airborne scale model was constructured and the measured sound-pressure levels used to evaluate baffle effectiveness. The same method was applied to a ficticious sonar array and the measured levels were used to compute the sonar response as the beam was steered from 0° to 360°. The pure-tone source frequency and baffle length were varied to examine their contribution on baffle effectiveness. The average reduction in sonar response, over the front 180°, was used to evaluate baffle effectiveness.

Noise Caused by the Spinning Machinery and Its Prevention

This article aims to prevent the noise of the textile machinery. An experiment has been made to investigate the generation mechanism of the impact noise caused by the textile machinery and by their gear systems. An attempt has also been made to prevent the propagation of the vibration into each machinery part. The following conclusions have been obtained: (1) The machinery mechanisms should be improved not to propagate the rapid variation of an acceleration and of a force.(2) Damping materials and lubricants ahould be used to reduce the mechanical vibration.(3) The vibration-proof isolators should be inserted between the vibration source and the machinery parts to prevent the propagation of vibrations into the machinery parts.

Machinery Noise on Logging Operations in Mixed Woodlands

A statistical picture has been obtained of the noise produced by different types of machines employed on logging operations in typical forested areas of eastern Ontario and western Quebec. Noise levels were measured at the operator's ear, at 15 and 50 ft, and at greater distances while the machines were being operated normally. Thus state-of-repair, idiosyncrasy of operators, topographical conditions, etc., were accepted as they came and no attempt was made to approximate, or correct to, standard test conditions. It was found that chain-saw operators, with some exceptions, and skidder operators, with few exceptions, are working in noise levels exceeding the CHABA criteria for hearing-damage risk. This risk does not exist for operators of slashers, loaders, and other equipment. Noise from logging operations is just inaudible at a distance of 112 miles under average conditions. Where machine noise is of concern, e.g., to recreationists, logging operations should probably be kept at a minimum distance of 1 mile.

Control of Noise from Machinery

At the session on machinery noise at the Purdue Noise Control Conference, seven papers were presented dealing mainly with the acoustic information needed for the proper selection and application of machines to meet appropriate acoustic specifications. Blazier's paper dealt with noise from large centrifugal compressors used in air conditioning systems. Schuder's paper dealt with the prediction and abatement of noise from high pressure gas control valves. Mitchell presented the purchasers's and manufacturers's views on noise specifications for gear transmissions. Faulkner's paper reported research into the radiation of noise from hermetic refrigeration compressors. Tseo provided information for estimating the performance of wall structures used for controlling machinery noise. Szerlag discussed the factors involved in the noise generation of hydraulic components. Hubert reported results of extensive studies of flow noise of grilles.

On the Noise of Farm Machinery and its Effects on Human Performance

On the Noise of Farm Machinery and its Effects on Human Performance

Noise and Vibration of Chain Saws

Experiments have been performed to assess the risks, to professional chainsaw operators, of permanent hearing loss and of traumatic vasospastic disease (TVD) resulting from exposure to excessive vibration (Raynaud's disease). A chain saw, which a survey of machinery noise on logging operations revealed to be typical (see preceding abstract), was mounted on a dynamometer without its bar or chain. Eliminating exhaust and intake noise reduced the level at the operator's ear by 24 dBA from the open exhaust configuration when the saw was mounted on the dynamometer, and by at least 18 dBA when cutting wood. The exposure to noise of several operators during normal logging operations was measured as a function of time and found to be greater than that permitted by either the Walsh-Healey or CHABA criteria. Effective exhaust and intake mufflers would remedy this situation. The vibration of the handles was examined when sawing hard and soft woods, and the levels obtained for two chain saws of convention construction were similar and in excess of European criteria for the onset of TVD. A third saw that possessed shock-mounted handles generated acceptable vibration levels.

Discussion: “Machinery Noise May Indicate Loss of Efficiency and Severity of Dynamic Stresses” (Underwood, A. C., and Graff, W. J., 1971, ASME J. Eng. Ind., 93, pp. 703–708)

Discussion: “Machinery Noise May Indicate Loss of Efficiency and Severity of Dynamic Stresses” (Underwood, A. C., and Graff, W. J., 1971, ASME J. Eng. Ind., 93, pp. 703–708)