EN 61260:1995
(Main)Electroacoustics - Octave-band and fractional-octave-band filters
Electroacoustics - Octave-band and fractional-octave-band filters
Provides performance requirements and methods for testing the performance of analogue, sampled-data, and digital implementations of bandpass filters that comprise a filter set or spectrum analyzer.
Elektroakustik - Bandfilter für Oktaven und Bruchteile von Oktaven
Electroacoustique - Filtres de bande d'octave et de bande d'une fraction d'octave
Fournit les prescriptions concernant les performances et les méthodes d'essai des filtres passe-bandes de conceptions analogiques, à données échantillonnées et numériques, y compris un ensemble de filtres ou un analyseur de spectre.
Elektroakustika - Oktavni, poloktavni in terčni filtri (IEC 61260:1995)
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Standards Content (Sample)
SLOVENSKI STANDARD
01-avgust-1998
(OHNWURDNXVWLND2NWDYQLSRORNWDYQLLQWHUþQLILOWUL ,(&
Electroacoustics - Octave-band and fractional-octave-band filters
Elektroakustik - Bandfilter für Oktaven und Bruchteile von Oktaven
Electroacoustique - Filtres de bande d'octave et de bande d'une fraction d'octave
Ta slovenski standard je istoveten z: EN 61260:1995
ICS:
17.140.50 Elektroakustika Electroacoustics
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
CEI
NORME
IEC
INTERNATIONALE
INTERNATIONAL
Première édition
STANDARD First edition
1995-07
Electroacoustique -
Filtres de bande d'octave et de bande
d'une fraction d'octave
Electroacoustics -
Octave-band and fractional-octave-band filters
Copy"right — all rights reserved
Droits de reproduction réservés —
© CEI 1995
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1260 ©IEC:1995 - 3 -
CONTENTS
Page
FOREWORD 5
Clause
1 Scope 7
2 Normative references 7
3 Definitions 9
17 4 Performance requirements
29 5 Test methods
Instrument marking 6
7 Instruction manual
Tables
1 Limits on relative attenuation for octave-band filters
A.1 Midband frequencies for octave-band and one-third-octave-band filters in
the audio range
B.1 Limits on relative attenuation for one-third-octave-band filters
Figure 1 - Illustration of minimum and maximum limits on relative attenuation for
class 1 octave-band filters
Annexes
A Midband frequencies
B Normalized frequencies at breakpoints of limits on minimum and maximum
relative attenuation for one-third-octave-band filters
ormance characteristics
C Recommendations for verification of the electrical pe rf
of bandpass filters
1260 ©IEC:1995 - 5 -
INTERNATIONAL ELECTROTECHNICAL COMMISSION
ELECTROACOUSTICS -
OCTAVE-BAND AND FRACTIONAL-OCTAVE-BAND FILTERS
FOREWORD
The IEC (International Electrotechnical Commission) is a worldwide organization for standardization
1)
comprising all national electrotechnical committees (IEC National Committees). The object of the IEC is to
promote international cooperation on all questions concerning standardization in the electrical and
electronic fields. To this end and in addition to other activities, the IEC publishes International Standards.
Their preparation is entrusted to technical committees; any IEC National Committee interested in
the subject dealt with may participate in this preparatory work. International, governmental and
non-governmental organizations liaising with the IEC also participate in this preparation. The IEC
collaborates closely with the International Organization for Standardization (ISO) in accordance with
conditions determined by agreement between the two organizations.
The formal decisions or agreements of the IEC on technical matters, prepared by technical committees on
2)
which all the National Committees having a special interest therein are represented, express, as nearly as
possible, an international consensus of opinion on the subjects dealt with.
They have the form of recommendations for international use published in the form of standards, technical
3)
reports or guides and they are accepted by the National Committees in that sense.
In order to promote international unification, IEC National Committees undertake to apply IEC International
4)
Standards transparently to the maximum extent possible in their national and regional standards. Any
divergence between the IEC Standard and the corresponding national or regional standard shall be clearly
indicated in the latter.
The IEC provides no marking procedure to indicate its approval and cannot be rendered responsible for any
5)
equipment declared to be in conformity with one of its standards.
International Standard IEC 1260 has been prepared by IEC technical committee 29:
Electroacoustics.
This standard supersedes IEC 225 published in 1966.
The text of this standard is based on the following documents:
DIS Report on voting
29/292/DIS 29!304/RVD
rt
Full information on the voting for the approval of this standard can be found in the repo
on voting indicated in the above table.
Annexes A, B and C are for information only.
1260 © IEC:1995 - 7 -
ELECTROACOUSTICS -
OCTAVE-BAND AND FRACTIONAL-OCTAVE-BAND FILTERS
1 Scope
1.1 This International Standard provides performance requirements and methods for
rf
testing the pe ormance of analogue, sampled-data, and digital implementations of band-
pass filters that comprise a filter set or spectrum analyser. The extent of the passband
region of a filter's relative attenuation characteristic is a constant percentage of the
midband frequency for all filters of a given bandwidth. An instrument complying with the
requirements of this International Standard may contain any number of bandpass filters
covering any desired frequency range.
1.2 Pe rformance requirements are provided for three filter classes designated class 0,
class 1, and class 2. Allowed tolerances increase as the class number increases.
rf
1.3 Bandpass filters complying with the pe ormance requirements of this standard may
be part of various measurement systems or may be an integral component of a specific
instrument and shall operate in real time. Performance requirements apply to any method
that is selected by the manufacturer to implement the design of the filters.
1.4 Instruments complying with the requirements of this standard are capable of provid-
ing frequency-band-filtered spectral information for a wide variety of signals, for example,
time-varying, intermittent, and steady; broadband and discrete frequency; and long and
short durations. For applications involving transient signals, different realizations of filters
meeting the requirements of this standard may give different results.
2 Normative references
The following normative documents contain provisions which, through reference in this
text, constitute provisions of this International Standard. At the time of publication, the
editions indicated were valid. All normative documents are subject to revision, and pa rties
to agreements based on this International Standard are encouraged to investigate the
possibility of applying the most recent editions of the normative documents indicated
below. Members of the IEC and ISO maintain registers of currently valid International
Standards.
IEC 50(801): 1994, International Electrotechnical Vocabulary (1EV) - Chapter 801:
Acoustics and electro-acoustics
IEC 651: 1979, Sound level meters
Amendment 1: 1993
IEC 801-2: 1991, Electromagnetic compatibility for industrial-process measurement and
control equipment - Part 2: Electrostatic discharge requirements
1260 ©IEC:1995 - 9 -
Electromagnetic compatibility for industrial-process measurement and
IEC 801-3: 1984,
control equipment - Part 3: Radiated electromagnetic field requirements
IEC 804: 1985, Integrating-averaging sound level meters
Amendment 1, 1989
Amendment 2, 1993
ISO 266: 1975, Acoustics - Preferred frequencies for measurements
OIML: 1978, Vocabulary of legal metrology - Fundamental terms
3 Definitions
For the purpose of this International Standard, the following definitions apply.
NOTE – For definitions of additional terms in this standard, reference should be made to IEC 50(801) and
the OIML Vocabulary of legal metrology.
3.1 bandpass filter: Filter with a single transmission band (or passband with small
relative attenuation) extending from a lower bandedge frequency greater than zero to a
finite upper bandedge frequency.
Nominal frequency ratio of 2:1; general symbol G.
3.2 octave ratio:
NOTES
1 This standard permits two options, designated base-ten and base-two, for determining an octave-band,
or fractional-octave-band, frequency ratio.
2 For base-ten systems,
3/10 (1)
G = 10
3 For base-two systems,
G2 = 2 (2)
4 The base-ten system is preferred.
3.3 bandwidth designator: Reciprocal of a positive integer, including 1, to designate
the fraction of an octave band; symbol 1/b.
Frequency of 1 000 Hz, exactly; symbol fr.
3.4 reference frequency:
3.5 exact midband frequency: In hertz, a frequency that has a specified relationship to
the reference frequency such that the ratio of the exact midband frequencies of any two
contiguous bandpass filters is the same for all filters in a filter set of a specified
. When the denominator of the bandwidth designator is an odd
bandwidth; symbol fm
number, exact midband frequencies of any filter in a set of filters are determined from:
fm = (Gxlb ) (
fr) (3)
and when the denominator of the bandwidth designator is an even number, exact midband
frequencies of any filter in a set of filters are determined from:
m = (G(2x+1)/(2b)) (fr)
(4)
where x is any integer, positive, negative, or zero.
1260 ©IEC:1995 - 11 -
NOTES.
1 Exact midband frequencies determined from equation (3) or (4) permit the output of narrow-fractional-
octave-band filters to be combined to yield the band level of a filter of wider-bandwidth with a corresponding
exact midband frequency and corresponding bandedge frequencies.
2 With the base-ten system, midband frequencies included within any 10:1 frequency range are the
same as within any other 10:1 frequency range except for the position of the decimal sign. With the
base-two system, midband frequencies are unique and do not repeat.
3 As examples, for one-third-octave-band filters, the exact midband frequency for the band with a
nominal midband frequency of 5 000 Hz is 5 011,872 Hz to three decimal places by the base-ten system
and 5 039,684 Hz by the base-two system, or a difference of approximately 0,6 %. At a nominal midband
frequency of 50 000 Hz, the exact midband frequency is 50 118,723 Hz by the base-ten system and
50 796,834 Hz by the base-two system, or an approximate difference of 1,4 %.
4 When the denominator of the bandwidth designator is an odd number, one of the filters in a complete
filter set may have a midband frequency of 1 000 Hz. When the denominator of the bandwidth designator
is an even number, the bandedge frequency of one adjacent pair of filters in a complete filter set may be
at 1 000 Hz and therefore none of the filters will have a midband frequency of 1 000 Hz.
5 Exact midband frequencies for octave-band and one-third-octave-band filters are given in table A.1 for
the usual range of audio frequencies.
In hertz, rounded midband frequencies for the
3.6 nominal midband frequencies:
designation of bandpass filters.
3.7 In hertz, frequencies of the lower and upper edges of the
bandedge frequencies:
passband of a bandpass filter such that the exact midband frequency is the geometric
mean of the lower and upper bandedge frequencies; symbols f1 and f2, respectively.
Bandedge frequencies are determined from:
-1/(2b)
fi = (G
) (fm ) (5)
and
(G+1!(2b)) (
=
f2
m) (6)
where
G represents an octave frequency ratio calculated according to equation (1) for base-
ten systems or (2) for base-two systems;
fm is an exact midband frequency determined from equation (3) or (4).
3.8 normalized frequency: For a bandpass filter, ratio of frequency to the exact mid-
band frequency; symbol film.
filter bandwidth: In hertz, for a given filter, upper bandedge frequency f 2 minus the
3.9
corresponding lower bandedge frequency Li calculated from equations (5) and (6).
Bandpass filter for which the nominal ratio of upper bandedge
3.10 octave-band filter:
frequency to lower bandedge frequency is two.
- 13 -
1260 © IEC:1995
Bandpass filter for which the ratio of upper band-
3.11 fractional-octave-band filter:
is an octave ratio raised to an exponent
edge frequency f2 to lower bandedge frequency f
equal to the applicable bandwidth designator.
NOTE – In symbols, a bandedge frequency ratio is f2/f, = Gvb.
In decibels, for a bandpass filter, at any frequency, the level
3.12 filter attenuation:
of the time-mean-square input signal minus the level of the indicated time-mean-square
A.
output signal, with both signal levels relative to the same reference quantity; symbol
in , in decibels, is represented by:
NOTE – In symbols, a time-mean-square input signal level L
/T) T V, (t) dt]l Vô) dB
Lin = 101g I[(1 (7)
J
where
t;
(t) is the instantaneous input signal as a function of time
Vin
is the elapsed time for integration;
T
V0 is an appropriate reference quantity such as 20 µV.
A corresponding expression applies for the level of the time-mean-square output signal.
In decibels, for all bandpass filters in an instrument,
3.13 reference attenuation:
nominal filter attenuation in the passband as specified by the manufacturer for determining
relative attenuation; symbol
Aref•
In decibels, for a bandpass filter, at any frequency, filter
3.14 relative attenuation:
attenuation minus the reference attenuation; symbol AA.
relative attenuation EA(f/f m ), in decibels, is determined from:
NOTE – At any normalized frequency 111m ,
DA(f/fn) = A(f/f m
) – Aref
(8)
where
f/m;
A (f/fm) is the filter attenuation at normalized frequency
is the reference attenuation.
Aref
are calculated from equation (3) or (4).
Exact midband frequencies fm
effective bandwidth: For constant-amplitude sinusoidal electrical input
normalized
3.15
signals, integral over normalized frequency of the ratio of the time-mean-square signal
indicated by the
...
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