IS 1890-7 (1995): Quantities and Units, Part 7: Acoustics [MSD 10: Social Responsibility]

इंटरनेट मानक

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.

“जान का अधकार, जी का अधकार” “परा को छोड न तरफ” Mazdoor Kisan Shakti Sangathan Jawaharlal Nehru “The Right to Information, The Right to Live” “Step Out From the Old to the New”

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“ान एक ऐसा खजाना जो कभी चराया नह जा सकताह ै”ै Bhartṛhari—Nītiśatakam “Knowledge is such a treasure which cannot be stolen”

IS 1890 (Part 7) : 1995 IS0 31-7 : 1992 *m

m*FfJFf &7 wTR?a (mg;TfteToT1 Indian Standard QUANT-ITIES AND UNITS

PART 7 ACOUSTICS

( First Revision )

UDC 53: 081

@ BIS 1995

BUREAU OF INDIAN STANDARDS MANAK BHAVAN, 9 BAHADUR SHAH ZAFAR MARG NEW DELHI 110002

September 1995 Price Group 6 Basic Standards Sectional Committee, MSD 1

NATIONAL FOREWORD

This Indian Standard (Part 7) (First Revision) which is identical with IS0 31-7 : 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 the current practice is to use a point (.) as the decimal marker.

Wherever the words ‘International Standard’ appear, referring to this standard, they should be read as ‘Indian Standard’.

This standard was first published in 1983. 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 Corresponding Indian Degree of Standard Standard Equivalence

ISO~31_0 : 1992 IS 1890 (Part 0) : 1995 Quantities and units : Part 0 Identical General principles (first revision) IS0 31-1 : 1992 IS 1890 (Part 1) : 1995 Quantities and units : Part 1 Space Identical and time (third revision) IS0 31-2 : 1992 IS 1890 (Part 2) : 1995 Quantities and units : Part 2 Identical Periodic and related phenomena (second revision) IS0 31-3 : 1992 IS 1890 (Part 3) : 1995 Quantities and units : Part 3 Identical Mechanics (second revision) IS0 31-4 : 1992 IS 1890 (Part 4) : 1982* Quantities, units and symbols Technically Part 4 Heat (first revision) Equivalent IS0 31-5 : 1992 IS 1890 (Part 5) : 1995 Quantities land units : Part 5 Identical Electricity and magnetism (first revision) IS0 31-6 : 1992 IS 1890 (Part 6) : 1993* Quantities, units and symbols : Technically Part 6 Light and related electromagnetic radiations Equivalent IS0 31-7 : 1992 IS 1890 (Part 7) : 1995 Quantities and units : Part 7 Identical Acoustics (first revision) IS0 31-8 : 1992 IS 1890 -(Part 8) : 1995 -Quantities and units : Part 8 Identical Physical chemistry and molecular physics (first revision) IS0 31-9 : 1992 IS 1890 (Part 9) : 1995 Quantities and units : Part 9 Atomic Identical and nuclear physics (first revision)

(Continued on third cover)

IS 1890 (Part 7) : 1995 IS0 31-7: 1992

hdian Standard QUANTITIES AND UNITS

PART 7 ACOUSTICS

( First Revision )

1 Scope maintain registers of currently valid International Standards. This part of IS0 31 gives names and symbols for quantities and units of acoustics. Where appropriate, IS0 16: 1975, Acoustics - Standard tuning frequency conversion factors are also given. (Standard musical pitch).

IS0 31-2:1992, Quantities and units - fart 2: Per- 2 Normative references iodic and related phenomena.

The following standards contain provisions which, IS0 131 :I 979, Acoustics - Expression of physical through reference in this text, constitute provisions and subjective magnitudes of sound or noise in air. 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 3 Names and symbols part of IS0 31 are encouraged to investigate the possibility of applying the most recent editions of the The names and symbols for quantities and units of standards indicated below. Members of IEC and IS0 acoustics are given on the following pages.

IS 1890 (Part 7) : 1995 IS0 31-7 : 1992

\COUSTICS Quantities

Item Quantity Symbol Definition Remarks MO.

'-1 period, T Time of one cycle periodic time

‘-2 frequency Jv f= l/T For the standard tuning frequency (standard musical pitch), see IS0 16.

‘-3 frequency interval For two tones, the~binary log- arithm of the ratio of the higher frequency to the lower frequency

‘-4 angular frequency, w 0 = 27cf pulsatance

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, u a-l/A The vector quantities u and k 4 wavenumber corresponding to repetency ant angular repetency are called wave vector and propagation vector respectively. 7-7 angular repetency, k k = 2~ j 7-6.7) angular wavenumber

7-8 volumic mass, e Mass divided by volume (7-7. 7) mass density, density

2 IS 1890 (Part 7) : 1995 IS0 31-7: 1992

Jnits ACOUSTICS

International Item Name of unit symbol for Definition Conversion factors and remarks No. unit

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. q______------_------_ 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

-1 7-4.b reciprocal S second, second to the power minus one

7-5.a metre m

7-6.a reciprocal metre, m-’ metre to the

power minus one -- 7-7.a radian per metre rad/m

7-7.b reciprocal metre, m-’ metre to the power minus one

7-8.a kilogram per kg/m3 cubic metre

3 IS 1890 (Part7) : 1995 IS0 31-7-z 1992

rcACOUSTICS (continued) Quantities

item Quantity Symbol Definition Remarks No.

7.-9.1 static pressure Ps Pressure that would exist in the (; 7-8.1) 3 absence of sound waves

7,-9.2 (instantaneous) Pt (p,) Difference between the instan- When any of the quantities i; 7-8.2) sound pressure taneous total pressure and the 7-9.2 to 7-13 inclusive is per- static pressure iodic, its symbol is often used without modification for its 7.-10 (instantaneous) rt (XI Instantaneous displacement of root-mean-square (r.m.s.1 value. t;“9. I) sound particle a particle in a medium from displacement what would be its position in the absence of sound waves

7 -11 (instantaneous) u. v at t;7-10. I) sound particle U=at velocity

au 7 -12 (instantaneous) a a=at (;7-l 1. I) sound particle acceleration

7‘-13 (instantaneous) Q, u, (4v) Instantaneous rate of volume ( 7-12. I) volume flow rate flow due to a sound wave

w 7‘-14.1 velocity of sound, c, Cc,) c=---_= lf k ( 7-13.7) (phase velocity)

dw 7‘-14.2 group velocity cs CQ = dk (--1

7‘-15 sound energy Mean sound energy in a given If the energy density varies w, (WJ, ( 7- 14. I) density, (e) volume divided by that volume 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 i17-15. 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 IS 1890 (Part 7) : 1995 IS0 31-j: 199i

Jnits ACOUSTICS (continued)

International item Name of unit symbol for Definition Conversion factors and remarks No. 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-12.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 J/m3 metre

7-l 6.a watt W

7-l 7.a watt per square W/m* metre

5 IS 1890 (Part 7) : 1995 IS0 31-7 : 1992

4COUSTICS (continued) Quantities

Item No. Quantity Symbol Definition Remarks

7-18 acoustic impedance & At a surface, the complex re- In definitions 7-l 8 to 7-20.2, 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.

7-19 mechanical z, At a surface (or at a point), the & = -$ &=A& impedance complex representation of total where A is the area of the sur- force divided by the complex face considered. representation of average par- title velocity at that surface (or of particle velocity at that point) in the direction of the force

7-20.1 surface density of Z, At a surface, the complex re- 17-77.2) mechanical presentation of sound pressure impedance divided by the complex representation of particle velocity

7-20.2 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

7-2 1 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 sub- square 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.

7-22 sound power level L,+, L, T + In(p/p,) = See also IS0 31-2:1992, item (721.7) No. 2-10. + In 10 . lg(P/Po)

where P is the root-mean- square 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 ( 7-22.7) time r given by F(r) = Ae-” cos [o(t - to)] then 6 is the damping coefficient

6 IS 1890 (Part 7) : 1995 IS0 31-7 : 1992

Jnits ACOUSTICS (continued

international item Name of unit symbol for Definition Conversion factors and remarks No. 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

_-______-_------_----- 7-21 .a bet B 1 B is the sound pressure See the introduction, subclause level when 2 lg(&,,) = 1 0.5.2. Instead of the bel, B, the sub- multiple 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,) = 1 0.5.2. Instead of the bel, B, the sub- multiple decibel, dB, is commonly used. Generally L, = lg(P&) B = 10 lg(P/P,) dB.

-1 7-23.a reciprocal S second, second to the power minus one ---.------__-___---__---___

7-23.b neper per second Np/s

7 IS l-890 (Part 7) : 1995 IS0 31-7 : 1992

ACOUSTICS (continued) Quantities

Item Quantity Symbcil Definition Remarks No.

T-24 time constant, t z = l/6 7-23.1) relaxation time where 6 is the damping coefficient

7-25 logarithmic A Product of damping coefficient 7-24.7) decrement and period.

A = 6T

r-26.1 attenuation CL If a quantity is a function of The quantity l/cr is called the 7-25.7) coefficient distance x given by attenuation length. F(x) = AeFa cos [0(x - q-J] m = 2a is called the power at- then a is the attenuation coef- tenuation coefficient. ficient and fl is the phase coef- When there is risk of confusion ficient with 7-27.4, m/2 is used instead of a for the attenuation coefficient.

7-26.2 phase coefficient /_I The quantity fl(x - xc,) is called I7-25.2) the phase.

7-26.3 propagation Y y=a+jp k=-jy ( 7-25.3) coefficient is the complex angular wavenumber.

7-27.1 dissipation factor, Ratio of the dissipated sound (7-26.7) dissipance power to the incident sound power

7-27.2 reflection factor, r, (e) Ratio of the reflected sound (7-26.2) reflectance power to the incident sound power

7-27.3 transmission factor, ‘E Ratio of the transmitted sound d+r+z=l (7-26.3) transmittance power to the incident sound power

7-27.4 absorption factor, 4, (a,) Ratio of the dissipated and a=b+T (7-26.4) absorbance transmitted sound power to the incident sound power

7-28 sound reduction R R =-$- ln(l/,) = (7-27.7) index + In 10. Ig(l/z)

where 7 is the transmission factor

8 IS 1890 (Part 7) : 1995 IS0 31-7 : 1992 hits ACOUSTICS (continued)

International Item Name of unit symbol for Definition Conversion factors and remarks No. unit

-24.a second s

______.----_------25.a neper NP See the introduction, subclause 0.5.2.

-26.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 0.3.2.

______-----__---_-P--M------7-28.a bel B 1 B is the sound re- See the introduction, subclause duction index when 0.5.2. lg(l/T) = 1 Instead of the bel, B, the sub- multiple decibel, dB, is commonly used. Generally R = Ig(l/s) B = 10 Ig(i/s) dB.

9 IS 1890 (Part 7) : 1995 IS0 31-7 : 1992

JCOUSTICS (concluded) Quantities

item Quantity Symbol Definition Remarks No.

7-29 equivalent A In a diffuse sound field, that (7-28. I) absorption area of area of a surface having an ab- a 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 ( 7-29.1) sound energy density in an en- closure to decrease to lOa of its initial value (i.e. by 60 dB) after the source has stopped

7-3 1 loudness level LN LN = In (PeffbO) 1 kHz = See also IS0 31-2. (7-30.71 In 1o - 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 stand- ardized 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 IS 1890 (Part 7) : 1995 IS0 31-7: 1992

Jnits ACOUSTICS (concluded)

Item International Name of unit symbol for Definition Conversion factors and remarks No. unit

7-29.a square metre m2

7-30.a second s

-----_--_-_---_.--_____-_._--_----_ -__. 7-31 .a phon 1 phon is the loudness Generally

level when LN = 20 b (peffh) l kHz phon. 2 b @effh) 1 kHz = O* 1 For a pure tone of frequency 1 kHz, 1 phon Pl dB.

_----_------.----_--C~------7-32.a sone A standard relation between loudness in sones and loudness level in phons has been adopted for practica use and is given in IS0 131.

11 (Continuedfionz second cover)

IS0 31-10 : 1992 IS 1890 (Part 10) : 1995 Quantities and units : Part 10 Identical Nuclear reactions and ionizing radiation (Grst revision) IS0 31-11 : 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) IS0 31-12 : 1992 IS 1890 (Part 12) : 1995 Quantities and units : Pan 12 Identical Characteristic numbers (fir.& revision) IS0 31-13 : 1992 IS 1890 (Part 13) : 1983* Quantities, units and symbols : Technically Part 13 Solid state physics Equivalent

*Under Revision.

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Review of Indian Standards

Amendments are issued to standards as the need arises on the basis of comments. Standards are also reviewed periodically; a standard along with amendments is reaffirmed when such review indicates that no changes are needed; if the review indicates that changes are needed, it is taken up for revision. Users of Indian Standards should ascertain that they are in possession of~the latest amendments or edition by referring to the latest issue of ‘BIS Handbook’ and ‘Standards Monthly Additions’.

This Indian Standard has been developed from DOC : MSD 1( 90 ).

Amendments Issued Since Publication

Amend No. Date of Issue Text Affected

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