1、BRITISH STANDARD BS 5944-5: 1985 Measurement of airborne noise from hydraulic fluid power systems and components Part 5: Simplified method of determining sound power levels from pumps using an anechoic chamber UDC 62822:534.61+621.65:534.62BS5944-5:1985 This British Standard, having been prepared un
2、der the directionof the Machinery andComponents Standards Committee, was published underthe authority of theBoardofBSI and comes into effect on 31 July1985 BSI 10-1999 The following BSI references relate to the work on this standard: Committee reference MCE/18 Draft for comment84/76091DC ISBN 0 580
3、14515 8 Committees responsible for this British Standard The preparation of this British Standard was entrusted by the Machinery and Components Standards Committee (MCE/-) to Technical Committee MCE/18, upon which the following bodies were represented: Association of British Mining Equipment Compani
4、es Association of Hydraulic Equipment Manufacturers British Compressed Air Society British Hydromechanics Research Association British Steel Corporation British Telecommunications Department of Trade and Industry (National Engineering Laboratory) Electricity Supply Industry in England and Wales Fede
5、ration of Manufacturers of Construction Equipment and Cranes Health and Safety Executive Institution of Mechanical Engineers Machine Tool Industry Research Association Ministry of Defence National Coal Board The following bodies were also represented in the drafting of the standard, through subcommi
6、ttees and panels: Bath University Institution of Production Engineers Amendments issued since publication Amd. No. Date of issue CommentsBS5944-5:1985 BSI 10-1999 i Contents Page Committees responsible Inside front cover Foreword ii 0 Introduction 1 1 Scope 1 2 Definitions 1 3 Measurement uncertaint
7、y 2 4 Test environment 2 5 Instrumentation 2 6 Installation conditions for pump 2 7 Operating conditions 3 8 Location and number of sound measuring points 3 9 Test procedure 3 10 Calculation of pump mean sound pressure levels and sound power levels 4 11 Calculation of mean sound pressure level at a
8、reference distance 4 12 Information to be recorded 4 13 Test report 5 Appendix A Errors and classes of measurement 6 Appendix B Reference dimensions, axes and location of sound measuring points 6 Appendix C Corrections for pump sound power level 7 Appendix D Calculation of mean sound pressure level
9、at a reference distance 8 Figure 1 Key reference axes and dimensions 7 Table 1 Standard deviation of sound power level determination 2 Table 2 Allowable variations in test conditions 3 Table 3 Permissible systematic errors of measuring instruments as determined during calibration 6 Table 4 Coordinat
10、es of microphone locations 6 Publications referred to Inside back coverBS5944-5:1985 ii BSI 10-1999 Foreword This Part of BS5944 has been prepared under the direction of the Machinery and Components Standards Committee and is one of a group of British Standards related to the measurement of noise em
11、anating from hydraulic fluid power systems and components. It is intended that this standard will unify testing methods and enable the performance of different pumps to be compared on a common basis. The standard comprises the following Parts. Part 1: Method of test for pumps; Part 2: Method of test
12、 for motors; Part 3: Guide to the application of Part1 and Part2; Part 4: Method of determining sound power levels from valves controlling flow and pressure. Further Parts are planned. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standar
13、ds are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front cover, pagesi andii, pages1 to8, an inside back cover and a back cover. This standar
14、d has been updated (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover.BS5944-5:1985 BSI 10-1999 1 0 Introduction In hydraulic fluid power systems, power is transmitted and controlled through a liquid under pressure i
15、n a closed circuit. Pumps are components which convert rotary mechanical power into fluid power. During the process of converting mechanical power into hydraulic fluid power, airborne noise, fluid-borne vibrations and structure-borne vibrations are radiated from the pump. The airborne noise level of
16、 a hydraulic fluid power pump is an important consideration in component selection. The noise measurement technique should, therefore, be such as to yield accurate appraisals of these airborne noise levels. The determination of noise levels is complicated by the interactions which occur during noise
17、 measurement. The fluid-borne and structure-borne vibrations from the pump can be transmitted to the circuit and ultimately give rise to background airborne noise levels which could affect the determination of the pump airborne noise levels. The procedures described in this Part of BS5944 are intend
18、ed to measure only the airborne noise radiated directly from the pump under test. This standard closely follows the methods described in BS5944-1 and BS5944-2 but allows the use of alternative pump mounting and drive configurations which are simpler and cheaper to implement in an anechoic chamber. M
19、uch of the guidance given in BS5944-3 is equally applicable to this standard. The data obtained has been shown to be sufficiently accurate in industrial terms for frequency A weighted, octave and1/3 octave noise measurements. 1 Scope This Part of BS5944 describes procedures for the determination of
20、the sound power levels of a hydraulic fluid power pump, under controlled conditions of installation and operation, suitable for providing a basis for comparing the noise levels of pumps in terms of: a) A-weighted sound power level; b) octave band sound power levels. From these sound power levels, so
21、und pressure levels may be calculated for reporting purposes (seeclause11). For general purposes, the frequency range of interest includes the octave bands with centre frequencies between125Hz and8000Hz. This method is applicable to all types of hydraulic fluid power pumps operating under steady-sta
22、te conditions, irrespective of size, except for any limitations imposed by the size of the test environment (see clause4). NOTEThe titles of the publications referred to in this standard are listed on the inside back cover. 2 Definitions For the purposes of this Part of BS5944, the definitions given
23、 in BS661 apply together with the following. 2.1 free sound field a sound field produced in a homogeneous, isotropic medium free of boundaries NOTEIn practice, it is a field in which the effects of the boundaries are negligible over the frequency range of interest. 2.2 free-field over a reflecting p
24、lane a field produced by a source in the presence of one reflecting plane on which the source is located 2.3 free-field over two reflecting planes a field produced by a source in the presence of two mutually perpendicular reflecting planes 2.4 anechoic room a test room having boundaries which absorb
25、 essentially all of the incident sound energy over the frequency range of interest, thereby affording free-field conditions over the measurement surface 2.5 mean-square sound pressure the sound pressure averaged in space and time on a mean-square basis NOTEIn practice, this is estimated by space and
26、 time averaging over a finite path length or over a number of fixed microphone positions. 2.6 mean sound pressure level (L p ) ten times the logarithm to the base10 of the ratio of the mean-square sound pressure to the square of the reference sound pressure in decibels (dB) NOTEThe weighting network
27、 or the width of the frequency band used should always be indicated; for example, A-weighted sound pressure level, octave band sound pressure level. The reference sound pressure is204Pa. 2.7 sound power level (L w ) ten times the logarithm to the base10 of the ratio of a given sound power to the ref
28、erence sound power in decibels (dB)BS5944-5:1985 2 BSI 10-1999 NOTEThe weighting network or the width of the frequency band used should always be indicated. The reference sound power is1 pW. 2.8 volume of source under test the volume of the envelope of the whole pump under test 3 Measurement uncerta
29、inty With the exception of the measurement environment specified in4.1, use methods of measurement which tend to result in standard deviations which are equal to or less than those given in Table 1. To meet this requirement the engineering methods given in clause4 and Appendix A of BS4196-4:1981 sha
30、ll be used. 4 Test environment 4.1 Conduct the tests in an environment generally in accordance with that described in BS4196-4 and which provides “free-field” conditions over two mutually perpendicular reflecting planes, at least one of which extends beyond the projected area of the microphone measu
31、ring array. NOTEThe other reflecting surface, which will usually be formed by an acoustic enclosure over the pump mounting, may be smaller if required. Table 1 Standard deviation of sound powerlevel determination 4.2 Calibrate the acoustic test environment thus formed by the substitution technique.
32、NOTEA reference sound source meeting the requirements of BS4196-00 1)may be used for calibration purposes. Ascertain the environmental corrections for each frequency band of interest (see10.4). 5 Instrumentation 5.1 Use instrumentation to measure fluid flow, fluid pressure, pump speed and fluid temp
33、erature in accordance with the recommendations for “industrial class” accuracy of testing, i.e.classC given in Appendix A. 5.2 Use type2 instruments for acoustical measurements in accordance with BS5969. This instrumentation shall be in accordance with BS4196-4 for both performance and calibration.
34、6 Installation conditions for pump 6.1 Pump location Locate the pump with its mounting flange flush with one reflecting plane. Arrange the second reflecting plane to intersect the first at right angles as close to the pump as practicable. 6.2 Pump mounting 6.2.1 Use a method of mounting the pump tha
35、t will minimize the noise radiated as a result of pump vibrations. 6.2.2 Construct the mounting bracket of high damping material, or with sound damping and sound insulating material applied to the bracket as required. 6.2.3 If necessary, employ vibration isolation techniques, even if the pump is sec
36、urely mounted. 6.3 Pump drive Locate the drive motor outside the test space and drive the pump through flexible couplings and an intermediate shaft or isolate the motor in an acoustic enclosure. 6.4 Hydraulic circuit 6.4.1 Include in the circuit all oil filters, oil coolers, reservoirs and restricto
37、r valves as required to meet the pump hydraulic operation conditions (seeclause7). 6.4.2 Use test fluid and filtration in accordance with the manufacturers recommendations. 6.4.3 Install inlet and discharge lines having bores in accordance with the manufacturers recommended practice. Exercise extra
38、care when assembling inlet lines to prevent air leaking into the circuit. 6.4.4 Mount the inlet pressure gauge at the same height as the inlet fitting or calibrate for any height difference. Octave band centred on frequency of Standard deviation Hz 125 250 500 1000 to4000 8000 dB 5.0 3.0 2.0 2.0 3.0
39、 NOTE 1The standard deviations include the effects of allowable variations in the positioning of the measurement points and in the selection of any prescribed measurement surface, but exclude variations in the sound power output of the source from test to test. NOTE 2The A-weighted sound power level
40、 will, in most practical cases, be determined with a standard deviation of approximately2dB. 1) In preparation. In the meantime ISO/DIS3748, prepared by the International Organization for Standardization, may be used.BS5944-5:1985 BSI 10-1999 3 6.4.5 Select the lengths of pipe between the pump and t
41、he load valve which minimize setting up standing waves in the discharge line which can increase the sound radiated from the pump. NOTEIt has been found that a long length of hydraulic hose can minimize standing wave effects. 6.4.6 Use a stable load valve. NOTEUnstable load valves in the discharge li
42、ne can generate and transmit noise through the fluid and piping which can emerge as airborne sound at the pump. 6.4.7 Position the load valve as far as possible from the pump, preferably outside the test room, to minimize interaction. Locate the load valve close to the pump only when adequate contro
43、l of its acoustic performance can be provided. 6.4.8 Enclose all fluid lines and load valves in the test space within acoustic ducts and enclosures, as required, to meet the specified background noise suppression (see9.1). Use enclosures having a sound transmission loss of at least10dB at125Hz and g
44、reater loss at higher frequencies. 7 Operating conditions 7.1 Determine the sound power levels of the pump for any desired set of operation conditions (see10.4). 7.2 Maintain these test conditions during the test within the limits given in Table 2. 7.3 Test the pump in the “as delivered” condition t
45、ogether with any integral ancillary pumps and valves operating normally during the test, so as to include their noise contributions to the airborne noise level of the pump. Table 2 Allowable variations in test conditions 8 Location and number of sound measuring points Provide and locate measuring mi
46、crophones in a quadrispherical array in accordance with Appendix B. Centre the quadrispherical array at the intersection of the two reflecting planes, on the projected centre line of the pump. 9 Test procedure 9.1 Background noise measurements 9.1.1 Measure the background noise over the frequency ra
47、nge of interest that is present during the pump noise test which does not emanate from the pump itself. NOTEOver the frequency range of interest, the band sound pressure levels of this background noise should be at least6dB below the pump band sound pressure levels at each measurement point. 9.1.2 C
48、orrect for this background noise, if evidenced by measurement, by applying the corrections for this purpose given in BS4196-4. 9.1.3 When measuring band levels of background noise is not practical, ensure that the A-weighted background sound level of each measurement point is at least6dB below the p
49、ump A-weighted sound level. Correct these A-weighted measurements for background noise. NOTE 1Easing the requirements for background noise levels can lead to an overestimate of the pump band sound pressure levels. NOTE 2The A-weighted background sound level at each measurement point may be checked by covering the pump with sound insulating materials capable of a transmission loss of at least10dB over the frequency range which is “determining” the A-weighted sound level of the pump. 9.1.4 If the background level is found to be too high, check for further n
