1、THE ENGINEERING EQUIPMENT ANO MATERIALS USERS ASSOCIATION NOISE A Guide to Information Required from Equipment Vendors PUBLICATION No. 104 - 1985 I EEMUAI ? * THE ENGINEERING EQUIPMENT AND MATERIALS USERS ASSOCIATION NOISE A Guide to Information Required from Equipment Vendors PUBUCATION NO. 704 - 1
2、985 Copyright 1985 The Engineering Equipment and Materiais Users. AssOCalOn 45 Beech Street London EC2Y 8AD Tel 0171 628 7878 Fax 0171 628 7862 e-ma;. 1 saleseemua - CO. iik website www.eemua.co.uk 1 EEMUAI - - - STD-EEMUA PUB NO 309-ENGL L995 D- chemical and energy industries. A list of Full and As
3、sociate Members (the latterbeing limited to membership of three technical committees) is given below. EEMUA is concerned with the design, installation, operation and maintenance of the engineering plant used by members in pursuing their business activities. ?le Association aims to reduce members? co
4、sts by providing the opportunity for them to share resources and expertise in order to keep abreast of technological developments and improve the effectiveness and efficiency of their engineering activities. EEMUA supports the British Standards Institution, works with other institutions, association
5、s, government departments, regulatory authorities and the Confederation of British Industry, and is also actively involved with other standards-making bodies, both national and international, such as the American Petroleum Institute. Work, whia is carried out in-house by members done or with the hel
6、p of other organisations, may lead to the production of Association publications. These are prepared primarily for members? use, but are usually offred for sale and thus for more general use. Such pubtications may also be submitted, normally thraugh the Bntkh standards Institution, as bases for appr
7、opriate national, European or international standards. A list of current EEMUA Publications which may be purchased from the Association is given at the en of this document. , Fui1 Members Associate Members Associated ctei BG BP Amoco Conoc0 - Caitex Petroleum Coming Esso?/ExxorrMobil . Foster Wheele
8、r Energy tem Generation FEu they may require a simple statement of the noise level at some defined position, or they may require a detailed report giving information on the noise emitted by the equipment at various frequencies and the noise levels under various modes of operation. If you are a manuf
9、acturer who has not been accustomed in the past to provide such information with your products you may find difficulty in answering the enquiries and you could, possibly, lose a customer. To provide a satisfactory answer you will have to make noise measurements and this will involve you either in tr
10、aining a member of your staff to make the measurements- and obtaining a sound-level meter- or contracting an outside consultant to make them. Either way you will need to understand what the measurements mean to ensure you get value for money and also to ensure that you are providing the information
11、your customer needs. The provision of reliable information on equipment noise may place a new burden upon you if you do not have an established procedure for noise tests. Although the user is ultimately responsible for the noise levels in his plant, legislation under consideration in the UK and EEC
12、may also place an obligation on the supplier to give satisfactory noise data with his product. But, even without this, there will be a growing trend for purchasers to insist on this information, so you will have to give consideration to setting up procedures for carrying out the necessary noise test
13、s. Appendix 3 gives a glossary of the more commonly used acoustic terms. For further reading, References 2 and 3 are recommended as useful guides to basic acoustic principles and methods of noise control. NOISE SPECIFICATIONS Many purchasers will now specify limits for noise emission in a purchase o
14、rder for equipment or in an enquiry. The Complexity of the specification will depend on how they intend to use the equipment. The first stage in the procedure could be a preliminary enquiry from a purchaser in the form of Appendix 1. This will enable him to make a general decision as to whether the
15、equipment will represent a noise problem or not. If the information he receives indicates that the noise will be well below the noise levels he requires in his plant, he may proceed with the purchase without further enquiry. On the other hand, if the information indicates that the equipment noise is
16、 approaching or exceeds his noise limits, he will require more detailed information. He may present a specification defining a naise limit in dB(A) at a certain distance from the equipment or at a particular place where an operator works. Alternatively, he may present a more detailed specification f
17、or noise limits such as that of Appendix 2 if the equipment is to be part of a complex plant containing other noisy equipment. In the example of Appendix 2 (based upon Reference 1) the purchaser will have started from the basis of the noise levels he wishes to meet in his plant, and possibly in the
18、neighbourhood as well. He will consider the total noise from all the equipment he is installing and will then allocate separate noise limits to each item. These will be quoted as sound-pressure levels and, possibly, as sound-power levels. The equipment would have to meet both sets of limits. As the
19、limits will have been derived for the particular situation in which the equipment is to operate, it is possible that different limits might be specified for the same equipment ordered for another purpose. It 1 may not be possible for standard equipment to meet the specified limits and the manufactur
20、er would then be asked to quote for silenced equipment or to indicate how his equipment could be silenced without impairing its performan. If noise-control measures cannot be supplied, the purchaser will use the noise data from the manufacturer to design his own noise control. In view of the diversi
21、ty of methods for obtaining sound-power levels (not all of which are satisfactory) the purchaser will probably define the test method by which the noise data should be obtained; at the very least he will want details of the test method by which the quoted data have been derived so that he can assess
22、 their quality. I MAKING NOISE MEASUREMENTS The noise level caused by a piece of equipment falls off with distance so it is important that any noise measurement should be accompanied by a note of the distance from the equipment. This could be the distance from the centre of the equipment or, for lar
23、ge equipment, it could be the distance from the equipment surface. It is common practice to make measurements at m from the equipment surface. For most equipment, a single measurement is not sufficient and it is necessary to take measurements at various positions around it. A purchaser may require t
24、o know the average of these measurements and the highest value; if there is a fixed operators position he may, in addition, require to know the noise level at that position. In many cases it may be sufficient to measure the A-weighted sound-pressure level in dB(A) at each position but some purchaser
25、s will also require measurements of the sound-pressure levels in octave bands. The measurements must be equivalent to those for the equipment operating in free field above a reflecting plane and if they are made in other surroundings it will be necessary to make a correction for the effect of the su
26、rroundings. There are various procedures for doing this given in standard test methods. A purchaser may require to use the equipment in other surroundings, say in a factory or engine room; alternatively he may wish to estimate the noise it causes in the neighbourhood. He will then require informatio
27、n on its noise emission in terms of the sound-power level in the various octave-bands so that he can estimate the noise in the circumstances in which he operates the equipment. Sound-power levels cannot be measured directly and they are calculated from measurements of sound-pressure level over an im
28、aginary surface around the machine, taking into account the area of the surface. Various standard procedures have been developed for doing this and a general description of these is given in Parts 2 and 3 of Reference 1. Specific procedures have been developed for certain types of equipment; BS 4999
29、 Part 51 : 1973, for example, is a test method for electric motors. c It will be evident on reading these test methods that some specialised knowledge is required for riving sound-power levds - and also for correcting sound-pressure levels to free-field values - so ore attempting to-obtain such nois
30、e data for your equipment you should seek specialist advice. ily. it must be emphasised that all these measurements may depend on the mode of operation of equipment. so if it can operate under various modes it will be necessary to provide separate noise data for each mode. SPECIAL NOISE CHARACTERIST
31、ICS Most of the noise emitted by machines is fairly evenly spread over a range of frequencies and is known as broad-band noise“. This is best illustrated in nature by the noise from a waterfall. But some machines emit characteristic noises such as whines or clanks and, while there is little evidence
32、 that these characteristics are more damaging to the hearing than broad-band noise, they can be extremely irritating to the listener (who may be an employee or a neighbour of the plant). A customer may require to take special measures to reduce such characteristic noises and will wish to know whethe
33、r the equipment he purchases emits them. STD-EEMUA PUB NO LO9-ENGL 1995 57bb734 0002OL3 O17 Tonal noise is not always evident from the usual noise measurements; even measurements in octave bands may not reveal the presence of tones which are eftremely evident to the ear, and special measurements are
34、 necessary which are too sophisticated for general industrial purposes. A subjective judgment must therefore be made by ear and a statement should be made in the noise report if the equipment emits a tone which is noticeable as a distinct pitch and represents a dominant feature of the total noise. A
35、 similar statement should be made for impulsive noise such as bangs and clanks. REFERENCES 1. Specification NWG-1 (Revision 2): Noise Procedure Specification, issued by the Oil Companies Materials Association, March 1980. Published by John Wiley these are indicated by asterisks. 1. * * mpucmoru OF N
36、OISE LIMITS The equipment noise limits listed in Table 1 and Table 2 have been selected so that the total plant noise generated shall not exceed the Purchasers requirements. These limits are specific to the items listed in this order. The sound-pressure level limits in Table 1 have been selected to
37、meet the work-area limits close to the equipment. They shall not be exceeded at any position around the equipment at a distance of Im or greater from its surface. The special Limits refer to the defined location. The sound-power level limits in Table 2 have been.selected to meet noise limits at loca
38、tions remote from the equipment. The equipment shall comply with the requirements of both Tables 1 and 2. These limits may be reduced if the equipment emits narrow-band or impulsive noise. If the equipment emits fluctuating or intermittent noise, the maximum level shall meet the specified . . . 3 li
39、mits. If the equipment emits slowly fluctuating or intermittent noise the.equivalent continuous sound level, for example, all readings taken.and any corrections applied, the measurement positions (with dimensioned sketch), the test environment, and the operating conditions of the equipment. The basi
40、s for any extrapolation shall be given. Any characteristic noise components such as narrow-band or impulsive noise and the octave bands in which the narrow-band noise occurs (a narrow-band component would be noticeable to the ear as a distinguishable pitch). The recommendations for the application o
41、f noise control to standard equipment to meet the Purchasers noise limits (where it is impractical to include low-noise features in the construction of the equipment). Any conflict with the requirements of other specifications for the equipment shall be stated. Details of noise-reduction features in
42、cluded in the supply. 7 Table 3 Tapulated data to be provided by the Vendor Octave-band centrefrequency(Hz) df3(A) 31.5 63 125 250 500 lk 2k 4k 8k* I Sound-pressure levels at lm (dB re 2 x N/mZ) 1 Average Maximum At specified position Position of maximum: I Component Sound-power levels (dB re l0-W)
43、1 1. 2. 3. Octave bands in which narrow-band noise is present: Method of test: (Attach separate sheet showing individual measurements and dimensioned sketch) Operating conditions: 4 8 APPENDIX 3: Glossary of Acoustic Terms THE DECIBEL (dB) Several acoustic quantities are denoted by the term “decibel
44、” and this is indicated by the use of the word “level” in the text; the most commonly used are “sound-pressure level” and “sound-power level”. The decibel is 10 times the logarithm of the quantity measured and, as a result, decibel values cannot be added and subtracted arithmetically; for example, a
45、dding two levels of 90dB gives a combined level of 93dB. The rules for adding decibels are given in text books and most standard test procedures. SOUND-PRESSURE LEVEL The loudness of a noise depends on the pressure variation of sound waves and this is measured as sound-pressure level, which is expre
46、ssed as decibels. SOUND-POWER LEVEL This is a measure of the noise energy emitted by the equipment. It is a basic characteristic of the equipment and therefore does not vary with distance or the reverberant nature of the surroundings. The actual radiated acoustic power is small, so it is internation
47、al practice to use the ratio of this power to 1 O- watt. It is then expressed in decibels so that it can be related to sound-pressure level in appropriate equations. For the same equipment the sound-power level in decibels is usually numerically greater than the sound-pressure level and it is import
48、ant not to confuse the two terms. FREQUENCY This is a measure of the pitch of a sound and the older unit of cycles per second has now been replaced by the designation hertz (Hz) or kilohertz (kHz1. A-WEIGHTING The human ear is not equally sensitive to all frequencies and we do not hear low-frequency
49、 sounds as weil as those in the mid-frequencies (500-1000 Hz). A sound-level meter can measure a wide range of frequencies with equal sensitivity of the ear. This is known as “A weighting” and measurements made with this filter switched in are denoted as dB(A). Most measurements of overall noise (that is, including all frequencies) are made as dB(A). OCTAVE BANDS The overall noise from a piece of equipment can be subdivided into the noise in various frequency regions to give more detailed information on the character of the noise; for example, whether it is
