Disclosure to Promote the Right To Information

Transcription

1 इ टरन ट म नक Disclosure to Promote the Right To Information Whereas the Parliament of India has set out to provide a practical regime of right to information for citizens to secure access to information under the control of public authorities, in order to promote transparency and accountability in the working of every public authority, and whereas the attached publication of the Bureau of Indian Standards is of particular interest to the public, particularly disadvantaged communities and those engaged in the pursuit of education and knowledge, the attached public safety standard is made available to promote the timely dissemination of this information in an accurate manner to the public. ज न1 क अ+धक र, ज 1 क अ+धक र Mazdoor Kisan Shakti Sangathan The Right to Information, The Right to Live प0र 1 क छ ड न' 5 तरफ Jawaharlal Nehru Step Out From the Old to the New IS (1995): Quantities and Units, Part 7: Acoustics [MSD 10: Social Responsibility]! न $ एक न' भ रत क +नम-ण Satyanarayan Gangaram Pitroda Invent a New India Using Knowledge! न एक ऐस खज न > ज कभ च0र य नहB ज सकत ह ह Bhartṛhari Nītiśatakam Knowledge is such a treasure which cannot be stolen

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4 IS : 1992 *m m*ffjff &7 wtr?a (mg;tftetot 1 Indian Standard QUANT-ITIES AND UNITS PART 7 ACOUSTICS ( First Revision ) UDC 53: BIS 1995 BUREAU OF INDIAN STANDARDS MANAK BHAVAN, 9 BAHADUR SHAH ZAFAR MARG NEW DELHI September 1995 Price Group 6

5 Basic Standards Sectional Committee, MSD 1 NATIONAL FOREWORD This Indian Standard (Part 7) (First Revision) which is identical with IS : 1992, issued by the International Organization for Standardization (ISO) was adopted by the Bureau of Indian Standards on the recommendation of the Basic Standards Sectional Committee (MSD 1) and approval of the Management and Systems Division Council. The text of the IS0 Standard has been approved as suitable for publication as Indian Standard without deviations. Certain conventions are, however, not identical to those used in Indian Standards. AtteJntion is particularly drawn to the following : Comma (J has been used as a decimal inarker while in Indian Standards is to use a point (.) as the decimal marker. the current practice Wherever the words International Standard appear, referring to this standard, they should be read as Indian Standard. This standard was first published in In this revision, following changes have been made: a) The decision by the International Committee for Weights and Measures (CIPM) in 1980 concerning the status of supplementary units has been incorporated; b) The special remark on logarithmic quantities and units has been elaborated; and c) The annex on CGS units has been deleted. ADDITIONAL INFORMATION IS 189O/ISO~31 consists of the following parts, under the general title Quantities and Units : International Standard ISO~31_0 : 1992 IS : 1992 IS : 1992 IS : 1992 IS : 1992 IS : 1992 IS : 1992 IS : 1992 IS : 1992 IS : 1992 Corresponding Indian Standard IS 1890 (Part 0) : 1995 Quantities and units : Part 0 General principles (first revision) IS 1890 (Part 1) : 1995 Quantities and time (third revision) and units : Part 1 Space IS 1890 (Part 2) : 1995 Quantities and units : Part 2 Periodic and related phenomena (second revision) IS 1890 (Part 3) : 1995 Quantities and units : Part 3 Mechanics (second revision) IS 1890 (Part 4) : 1982* Quantities, Part 4 Heat (first revision) units and symbols IS 1890 (Part 5) : 1995 Quantities land units : Part 5 Electricity and magnetism (first revision) IS 1890 (Part 6) : 1993* Quantities, units and symbols : Part 6 Light and related electromagnetic radiations Quantities and units : Part 7 Acoustics (first revision) IS (Part 8) : Quantities and units : Part 8 Physical chemistry and molecular physics (first revision) IS 1890 (Part 9) : 1995 Quantities and units : Part 9 Atomic and nuclear physics (first revision) Degree of Equivalence Identical Identical Identical Identical Technically Equivalent Identical Technically Equivalent Identical Identical Identical (Continued on third cover)

6 IS0 31-7: 1992 hdian Standard QUANTITIES AND UNITS PART 7 ACOUSTICS ( First Revision ) 1 Scope This part of IS0 31 gives names and symbols for quantities and units of acoustics. Where appropriate, conversion factors are also given. 2 Normative references The following standards contain provisions which, through reference in this text, constitute provisions of this part of IS0 31. At the time of publication, the editions indicated were valid. All standards are subject to revision, and parties to agreements based on this part of IS0 31 are encouraged to investigate the possibility of applying the most recent editions of the standards indicated below. Members of IEC and IS0 maintain registers of currently valid International Standards. IS0 16: 1975, Acoustics - (Standard musical pitch). Standard tuning frequency IS0 31-2:1992, Quantities and units - fart 2: Periodic and related phenomena. IS0 131 :I 979, Acoustics - Expression of physical and subjective magnitudes of sound or noise in air. 3 Names and symbols The names and symbols for quantities and units of acoustics are given on the following pages.

7 IS : 1992 \COUSTICS Quantities Item MO. Quantity Symbol Definition Remarks '-1 period, periodic time T Time of one cycle -2 frequency Jv f= l/t For the standard tuning frequency (standard musical pitch), see IS frequency interval For two tones, the~binary logarithm of the ratio of the higher frequency to the lower frequency -4 angular frequency, w pulsatance 0 = 27cf 7-5 wavelength 1 Distance in the direction of propagation of a periodic wave between two successive points where at a given time the phase is the same 7-6 repetency, 4 wavenumber u a-l/a The vector quantities u and k corresponding to repetency ant angular repetency are called wave vector and propagation vector respectively. 7-7 j 7-6.7) angular repetency, angular wavenumber k k = 2~ 7-8 volumic mass, e Mass divided by volume (7-7. 7) mass density, density 2

8 IS0 31-7: 1992 Jnits ACOUSTICS Item No. Name of unit International symbol for unit Definition Conversion factors and remarks 7 '-1.a second S 7-2.a hertz Hz 1 Hz= 1 s-' 1 Hz is the frequency of a periodic phenomenon of which the period is 1 s _ _ r-3.a octave The frequency interval The numerical value of the frequency between& andf, is one interval in octaves is given by octave if &/fi = 2 Ib(f,fiL ct; 2 A>. Ma radian per second rad/s 7-4.b reciprocal S -1 second, second to the power minus one 7-5.a metre m 7-6.a 7-7.a reciprocal metre, metre to the power minus one radian per metre m- rad/m b reciprocal metre, metre to the power minus one m- 7-8.a kilogram per cubic metre kg/m3 3

9 IS 1890 (Part7) : 1995 IS z 1992 rc ACOUSTICS (continued) Quantities item No. Quantity Symbol Definition Remarks (; 7-8.1) static pressure Ps Pressure that would exist in the 3 absence of sound waves 7, -9.2 i; 7-8.2) t; 9. I) (instantaneous) sound pressure (instantaneous) sound particle displacement Pt (p,) Difference between the instan- When any of the quantities taneous total pressure and the to 7-13 inclusive is perstatic pressure iodic, its symbol is often used without modification for its rt (XI Instantaneous displacement of root-mean-square (r.m.s.1 value. a particle in a medium from what would be its position in the absence of sound waves 7-11 (instantaneous) u. v at t; I) sound particle U=at velocity 7-12 (instantaneous) (; 7-l 1. I) sound particle acceleration a au a=at 7-13 (instantaneous) Q, u, (4v) Instantaneous rate of volume ( I) volume flow rate flow due to a sound wave velocity of sound, c, Cc,) ( ) (phase velocity) c=---_= w k lf group velocity (-1 cs CQ = dw dk 7-15 ( I) sound energy density, w, (WJ, (e) Mean sound energy in a given volume divided by that volume If the energy density varies with time, the mean must be volumic sound taken over an interval during energy which the sound may be considered statistically stationary. 7-l 6 sound power P, Pa Power emitted, transferred or i I) received as sound waves 7-l 7 sound intensity 1, J For unidirectional sound power, I (7-16. I) sound power through a surface normal to the direction of propagation divided by the area of the surface 4

10 IS0 31-j: 199i Jnits ACOUSTICS (continued) item No. International Name of unit symbol for Definition Conversion factors and remarks unit -9.a Pascal Pa bar (bar), 1 bar = 100 kpa (exactly) r-1 0.a metre m I-1 1.a metre per second ~m/s r-1 2.a metre per second m/s* squared 7-13.a cubic metre per m3/s second 7-14.a metre per second m/s 7-15.a joule per cubic metre J/m3 7-l 6.a watt W 7-l 7.a watt per square W/m* metre 5

11 IS : COUSTICS (continued) Quantities Item No. Quantity Symbol Definition Remarks acoustic impedance & mechanical z, impedance At a surface, the complex re- In definitions 7-l 8 to , the presentation of sound pressure quantities in the numerators divided by the complex repres- and denominators are assumed entation of volume flow rate to be sinusoidal. At a surface (or at a point), the & = -$ &=A& complex representation of total where A is the area of the surforce divided by the complex face considered. representation of average partitle velocity at that surface (or of particle velocity at that point) in the direction of the force surface density of Z, At a surface, the complex re ) mechanical presentation of sound pressure impedance divided by the complex representation of particle velocity characteristic z, At a point in a medium and for For a non-dissipative medium (7-77.1) impedance of a a plane progressive wave, the Z, = ce. medium complex representation of sound pressure divided by the complex representation of particle velocity sound pressure % Lp = In(P/po) = In 10 - lg(p/p,j The subscript p is often omit- (7-20.1) level where p is the root-mean- ted, especially when other subsquare value of the sound scripts are needed. pressure and the reference See also IS0 31-2:1992, item pressure p. is equal to 20 PPa No. -2-g sound power level L,+, L, T + In(p/p,) = See also IS0 31-2:1992, item (721.7) No In 10. lg(p/po) where P is the root-meansquare value of the sound power and the reference power PO isequal to 1 pw 7-23 damping coefficient 6 If a quantity is a function ~of ( ) time r given by F(r) = Ae- cos [o(t - to)] then 6 is the damping coefficient 6

12 IS : 1992 Jnits ACOUSTICS (continued item No. international Name of unit symbol for Definition Conversion factors and remarks unit -18.a Pascal second Pa - s/m3 per cubic metre I-1 9.a newton second N. s/m per metre 7-20.a Pascal second Pa - s/m per metre _- -_ _ a bet B 1 B is the sound pressure See the introduction, subclause level when 2 lg(&,,) = Instead of the bel, B, the submultiple decibel, db, is commonly used. Generally Lp = 2 lg(p/po) B = 20 1g@k,) db _ _ 7-22.a bel B 1 B is the sound power See the introduction, subclause level when lg(p/p,) = Instead of the bel, B, the submultiple decibel, db, is commonly used. Generally L, = lg(p&) B = 10 lg(p/p,) db a reciprocal S -1 second, second to the power minus one b neper per second Np/s 7

13 IS l-890 (Part 7) : 1995 IS : 1992 ACOUSTICS (continued) Quantities Item No. Quantity Symbcil Definition Remarks T-24 time constant, ) relaxation time t z = l/6 where 6 is the damping coefficient 7-25 logarithmic A Product of damping coefficient ) decrement and period. A = 6T r-26.1 attenuation CL If a quantity is a function of The quantity l/cr is called the ) coefficient distance x given by attenuation length. F(x) = AeFa cos [0(x - q-j] m = 2a is called the power atthen a is the attenuation coef- tenuation coefficient. ficient and fl is the phase coef- When there is risk of confusion ficient with , m/2 is used instead of a for the attenuation coefficient phase coefficient /_I The quantity fl(x - xc,) is called I7-25.2) the phase propagation Y y=a+jp k=-jy ( ) coefficient is the complex angular wavenumber dissipation factor, (7-26.7) dissipance reflection factor, (7-26.2) reflectance Ratio of the dissipated sound power to the incident sound power r, (e) Ratio of the reflected sound power to the incident sound power transmission factor, E (7-26.3) transmittance Ratio of the transmitted sound d+r+z=l power to the incident sound power absorption factor, (7-26.4) absorbance 4, (a,) Ratio of the dissipated and a=b+t transmitted sound power to the incident sound power 7-28 sound reduction R (7-27.7) index R =-$- ln(l/,) = + In 10. Ig(l/z) where 7 is the transmission factor 8

14 IS : 1992 hits Item No. ACOUSTICS (continued) International Name of unit symbol for Definition Conversion factors and remarks unit -24.a second s _.----_ a neper NP See the introduction, subclause a reciprocal metre, m- a and p are often given in Np/m and metre to the rad/m respectively. power minus one r-27.a one 1 See the introduction, subclause _-P--M a bel B 1 B is the sound re- See the introduction, subclause duction index when lg(l/t) = 1 Instead of the bel, B, the submultiple decibel, db, is commonly used. Generally R = Ig(l/s) B = 10 Ig(i/s) db. 9

15 IS : 1992 JCOUSTICS (concluded) Quantities item No. Quantity Symbol Definition Remarks 7-29 equivalent A In a diffuse sound field, that (7-28. I) absorption area of area of a surface having an aba surface or object sorption factor equal to 1, which, if diffraction effects are neglected, would, in the same diffuse sound field, absorb the same power 730 reverberation time T Time required for the average ( ) sound energy density in an enclosure to decrease to loa of its initial value (i.e. by 60 db) after the source has stopped loudness level LN LN = In (PeffbO) 1 khz = See also IS ( In 1 o - b (Peffhd 1 khz These are not purely physical where Peff is the root-mean- quantities, but entail subjective square value of the sound evaluation. pressure of a pure tone of 1 khz, which is judged by a normal observer under standardized listening conditions as being as loud as the sound under investigation, and where p. = 20 PPa 732 loudness N A normal observer s auditory (7-37.1) estimate of the ratio between the strength of the sound considered and that of a reference sound having a loudness level of 40 phons 10

16 IS0 31-7: 1992 Jnits Item No. ACOUSTICS (concluded) International Name of unit symbol for Definition Conversion factors and remarks unit 7-29.a square metre m a second s -----_--_-_---_.-- -_._--_----_ a phon 1 phon is the loudness Generally level when LN = 20 b (peffh) l khz phon. 2 1 khz = O* 1 For a pure tone of frequency 1 khz, 1 phon Pl db. _----_ _--C~ a sone A standard relation between loudness in sones and loudness level in phons has been adopted for practica use and is given in IS

17 (Continuedfionz second cover) IS : 1992 IS 1890 (Part 10) : 1995 Quantities and units : Part 10 Identical Nuclear reactions and ionizing radiation (Grst revision) IS : 1992 IS 1890 (Part 11) : 1995 Quantities and units : Part 11 Identical Mathematical signs and symbols for use in the physical science and technology (second revision) IS : 1992 IS 1890 (Part 12) : 1995 Quantities and units : Pan 12 Identical Characteristic numbers (fir.& revision) IS : 1992 IS 1890 (Part 13) : 1983* Quantities, units and symbols : Technically Part 13 Solid state physics Equivalent *Under Revision.

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