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1、BRITISH STANDARD BS 5331:1976 Method of test for Measurement of the physical properties of sonic bangs UDC 534.08:629.7016.54 Licensed Copy: sheffieldun sheffieldun, na, Fri Dec 01 14:21:17 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 5331:1976 This British Standard, having been prepared under the
2、direction of Engineering Divisional Council, was published under the authority of the Executive Board on 30 July 1976 BSI 10-1999 The following BSI references relate to the work on this standard: Committee reference E/1/5 Draft for comment 72/22825 DC ISBN 0 580 09491 X Cooperating organizations The
3、 Acoustics Committee, under whose supervision this British Standard was prepared, consists of representatives from the following Government department and scientific and industrial organizations: Association of Consulting Engineers British Broadcasting Corporation British Kinematograph Sound and Tel
4、evision Society British Radio Equipment Manufacturers Association Cinematograph Exhibitors Association of Great Britain and Ireland Department of Industry National Physical Laboratory* Engineering Equipment Users Association Incorporated Association of Architects and Surveyors Institution of Mechani
5、cal Engineers Institution of Municipal Engineers Institute of Acoustics Institute of Physics Institute of Sound and Vibration Research* Institution of Electronic and Radio Engineers Post Office Royal Institute of British Architects Society of British Aerospace Companies* Transmission Distributors As
6、sociation (BEAMA) The Government department and scientific and industrial organizations marked with an asterisk in the above list, together with the following, were directly represented on the committee entrusted with the preparation of this British Standard: Civil Aviation Authority British Airways
7、 Overseas Division Department of the Environment Department of Industry Ministry of Defence Medical Research Council Royal Aeronautical Society Amendments issued since publication Amd. No.Date of issueComments Licensed Copy: sheffieldun sheffieldun, na, Fri Dec 01 14:21:17 GMT+00:00 2006, Uncontroll
8、ed Copy, (c) BSI BS 5331:1976 BSI 10-1999i Contents Page Cooperating organizationsInside front cover Forewordii 1Scope1 2Definitions1 3Measuring system2 4Environmental conditions4 5Analysis of measurements4 Figure 1 Example of graphical display of a sonic bang in the vicinity of the ground3 Licensed
9、 Copy: sheffieldun sheffieldun, na, Fri Dec 01 14:21:17 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 5331:1976 ii BSI 10-1999 Foreword This British Standard has been prepared under the authority of the Engineering Divisional Council. This standard is based on, but not identical to ISO 2249 “Descrip
10、tion and measurement of physical properties of sonic booms”. Since the publication in 1973 of ISO 2249 further consideration has been given to this subject and the result of this work is reflected in this standard. A British Standard does not purport to include all the necessary provisions of a cont
11、ract. Users of British Standards 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, pages i and ii, pages 1 to 4 and a back cover.
12、This standard 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. Licensed Copy: sheffieldun sheffieldun, na, Fri Dec 01 14:21:17 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 5331:1976 BSI 10-19991
13、1 Scope This British Standard establishes the terminology and definitions for describing the physical properties of sonic bangs caused by overflight of supersonic aircraft, and specifies the minimum requirements of equipment and the method to be used for their measurement. The conditions of measurem
14、ent envisaged include those in which the direction and time of arrival of the pressure disturbance and even its approximate intensity are not necessarily known in advance. This standard provides the basis for the measurement and description of sonic bang pressure signatures suitable for evaluating t
15、heir effects on people, structures, animals and unstable terrain features. NOTEThe physical properties described by these procedures are properties of particular acoustic events (sonic bangs) occurring at a specified location. They cannot be considered as properties of a particular aircraft, since t
16、he measured quantities depend also on prevailing conditions of flight, of atmosphere and of ground. 2 Definitions For the purposes of this British Standard the following definitions apply. 2.1 sonic bang the acoustic event which is a manifestation of the shock wave system generated by an aircraft wh
17、en it flies at a speed greater than the local sound velocity; also called sonic boom an example of the graphical display (pressure signature) of a sonic bang in the vicinity of the ground, showing superposed incident and reflected waveforms, is illustrated in Figure 1, which may assist the understan
18、ding of the definitions given in 2.4 the event comprises bow and stern shocks, with a progressive pressure decrease between the occurrences of the two groups of shocks. Although the two groups of shocks may be heard separately, the whole event is conventionally described as a single sonic bang NOTEI
19、n practice the onset of a shock is usually well defined, but the termination is often subject to some uncertainty of interpretation and may have to be arbitrarily specified. 2.2 overpressure Symbol: p Unit: Pa the difference between the pressure at a point at any instant and the ambient atmospheric
20、pressure; the over-pressure is positive when the pressure is greater than the ambient atmospheric pressure, and negative when it is less 2.3 peak overpressure Symbol: pmax Unit: Pa the highest positive value of the overpressure 2.4 pressure signature the time history of the overpressure NOTEThe free
21、 field signature, when displayed graphically, often resembles the letter N and is then called an N-wave. 2.5 pressure rise Symbol: %p Unit: Pa the increase in pressure between the onset and the termination of a given shock 2.5.1 incident pressure rise Symbol: %pi Unit: Pa the pressure rise in the sh
22、ock wave which arrives direct at the measurement point without being affected by reflection from the ground or other objects 2.5.2 reflected pressure rise Symbol: %pr Unit: Pa the pressure rise in the shock wave which arrives at the measurement point after being reflected from the ground or other su
23、rfaces 2.6 free-field conditions conditions existing when the ground and other reflecting objects are remote enough so that their effects on the shock wave system are negligible. Quantities measured under free-field conditions are denoted by symbols with the subscript “f” 2.7 ground conditions condi
24、tions existing when reflecting objects (not including those in the plane of the ground or the ground itself) are remote enough so that their effects on the shock wave system are negligible. Quantities measured under ground conditions are denoted by symbols with the subscript “g” 2.8 ground reflectio
25、n coefficient Symbol: r a coefficient defined as the ratio of the reflected pressure rise to the incident pressure rise, both originating from the same ray Licensed Copy: sheffieldun sheffieldun, na, Fri Dec 01 14:21:17 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 5331:1976 2 BSI 10-1999 2.9 ground
26、 reflection factor Symbol: Kr a factor defined by the equation Kr= 1 + r NOTETheoretically, for a weak shock and a smooth rigid plane ground, Kr is equal to 2. 2.10 total duration of a sonic bang signature Symbol: %tt Unit: ms the time interval between the beginning and the end of the pressure signa
27、ture. For an N-wave type signature, it is the time interval between the onset of the bow shock and the termination of the stern shock NOTEAlthough it is often difficult to define precisely the termination of the sonic bang signature, it is of practical value to use an approximate total duration. 2.1
28、1 rise time of a shock Symbol: % Unit: ms the time interval between the onset of a shock and its specified termination 2.11.1 incident rise time Symbol: %i Unit: ms the time interval between the onset of a shock and its termination before the shock wave has been affected by reflection from the groun
29、d or other objects 2.11.2 reflected rise time Symbol: %r Unit: ms the time interval between the onset of a shock after being reflected from the ground or other surfaces and its specified termination 2.12 time-to-peak Symbol: %tm Unit: ms the time interval between the onset of the first bow shock and
30、 the occurrence of the peak overpressure 2.13 impulse Symbol: l Unit: mPa s for a given pressure signature, the integral of the over-pressure with respect to time from the start of the signature up to a given instant 2.13.1 maximum impulse Symbol: lmax Unit: mPa s algebraically the greatest value of
31、 the impulse 2.13.2 minimum impulse Symbol: lmin Unit: mPa s algebraically the least value of the impulse 2.14 Signature interval Symbol: %t Unit: ms the time interval between the onset of the first shock and the onset of the last shock in the signature 2.15 Characteristic overpressure Symbol: %pc U
32、nit: Pa a quantity defined by the following formula: 3 Measuring system 3.1 General requirements. A sonic bang pressure signature shall be sensed by a pressure-sensitive microphone (see 3.2). The signal from the microphone shall be amplified and recorded by a suitable recorder (see 3.3). The measuri
33、ng chain shall have an overall frequency response over the range of at least from 0.1 Hz to 5 000 Hz. The type of microphone capsule used depends on the measurement conditions. Where a free-field measurement is required, the free-field response of the capsule plus measuring chain shall be flat withi
34、n 2 dB; where the microphone is mounted in a baffle or flush with the ground, the pressure response of the capsule plus measuring chain shall be flat within 2 dB. The total harmonic distortion of the microphone and its associated amplifier shall not exceed 4 % at the maximum overpressure to be measu
35、red. 3.2 Microphone. The response of the microphone system above the frequency range of interest shall have a smooth roll-off in order to restrict overshoot distortion in the recording of sonic bangs with short rise time. NOTE 1The maximum dimension of the sensitive surface of the microphone determi
36、nes the degree of fineness with which the overpressure at a location can be measured. For most applications a dimension not exceeding 22 mm is recommended. NOTE 2Fully sealed capsules should be used with extreme caution to avoid pressure unbalance either in calibration or in measurement. NOTE 3The c
37、alibration at very low frequencies, i.e. below about 25 Hz, can be performed with a piston operating into a known volume in which the entire microphone capsule is placed. It is essential that the calibration circumstances are in accordance with those that prevail during the measurements. The sound p
38、ressure generated is calculated from the known excursion of the piston and from the volume, allowing for corrections for the transition from the adiabatic to the isothermal condition. %pc 4 %t - - lmaxlmin()= Licensed Copy: sheffieldun sheffieldun, na, Fri Dec 01 14:21:17 GMT+00:00 2006, Uncontrolle
39、d Copy, (c) BSI BS 5331:1976 BSI 10-19993 3.3 Recorder. The dynamic range of the recorder shall be at least 45 dB under the condition that the total harmonic distortion is less than 1 % measured at 1 000 Hz. NOTE 1Since accurate prediction of peak overpressures is difficult, the optimum system gain
40、setting cannot be predetermined. For this reason it is recommended to record more than one channel simultaneously with different gain settings at 5 dB or 10 dB intervals. This method will help in obtaining recordings of the sonic bang with adequate signal to noise ratio by utilizing the full dynamic
41、 range of at least one channel of the recording system. An overload indicator, which may be in the form of a peak reading meter or an automatically recorded overload indication, is desirable. NOTE 2The specified minimum dynamic range of the recorder may not be sufficient to permit full-range frequen
42、cy analysis of a sonic bang. For these measurements, it may be desirable to include pre-emphasis in one channel of the recording system to improve signal to noise ratio at the higher frequencies, the inverse de-emphasis being applied to the playback system during frequency analysis; such equalizatio
43、n should not be used for the recording and reproduction of the pressure signature, except where necessary to meet the frequency response requirement of the measuring chain in 3.1. 3.4 Equipment for unattended recording. For recording sonic bangs over a long period, specially designed data recorders
44、shall be used since conventional recording systems are limited in operation for this purpose. The recorder shall be capable of responding to transients instantaneously. Where operation is provided for predetermined times during the day and an immediate response to sonic bangs, appropriate control ci
45、rcuitry shall be used. The equipment shall be self-contained with associated signal conditioning networks. Appropriate calibration signals for each channel shall be provided and recorded on the equipment following each operational recording. The equipment shall comply as closely as possible with the
46、 requirements in 3.1, 3.2 and 3.3, and deviations shall be reported. 3.5 Microphone position 3.5.1 Measurement in ground conditions. The microphone shall be mounted with its axis perpendicular to the ground and its sensitive surface facing upwards and flush to the ground, with a tolerance of 3 mm. N
47、OTEThere are conditions when true flush mounting, such as with hard concrete surfaces, is impracticable. In such conditions the microphone should be mounted with its axis either perpendicular or parallel to the ground and its sensitive surface as close to the ground as possible, avoiding a face-down
48、 condition. The microphone body and associated equipment shall be either below ground level or so remote that their presence does not influence the measurements. Figure 1 Example of graphical display of a sonic bang in the vicinity of the ground Licensed Copy: sheffieldun sheffieldun, na, Fri Dec 01
49、 14:21:17 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 5331:1976 4 BSI 10-1999 3.5.2 Measurement in other conditions. Where measurements are to be carried out away from the ground they shall be made either with the diaphragm at right angles to the anticipated ray path, in which case the normal incidence free-field response applies, or with the diaphragm parallel to the anticipated ray path, in which case the grazing incidence free-field response applies. 3.5.3 Freedom from extraneous signals. Every effort shall be made to avoid intrusive electrica
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