IEC 61606-1:2009

IEC 61606-1 ®
Edition 2.0 2009-07
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Audio and audiovisual equipment – Digital audio parts – Basic measurement
methods of audio characteristics –
Part 1: General
Équipements audio et audiovisuels – Parties audionumériques – Méthodes
fondamentales pour la mesure des caractéristiques audio –
Partie 1: Généralités
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IEC 61606-1 ®
Edition 2.0 2009-07
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Audio and audiovisual equipment – Digital audio parts – Basic measurement

methods of audio characteristics –

Part 1: General
Équipements audio et audiovisuels – Parties audionumériques – Méthodes

fondamentales pour la mesure des caractéristiques audio –

Partie 1: Généralités
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 33.160.01 ISBN 978-2-8322-1005-5

– 2 – IEC 61606-1:2009  IEC 2009
CONTENTS
FOREWORD . 4
1 Scope . 6
2 Normative references . 6
3 Terms, definitions, explanations and rated values . 7
3.1 Terms and definitions . 7
3.2 Explanation of term “jitter” . 9
3.3 Rated values . 10
4 Measuring conditions . 10
4.1 Environmental conditions . 10
4.2 Power supply . 10
4.2.1 Supply voltage . 10
4.2.2 Frequency(ies) . 10
4.2.3 High-frequency and harmonic components (or ripples) in the power
supply output . 10
4.3 Test signal frequencies . 10
4.4 Standard setting . 11
4.4.1 Standard input conditions for the EUT . 11
4.4.2 Standard output conditions for the EUT . 12
4.4.3 Standard setting of controls . 12
4.5 Preconditioning . 12
4.6 Measuring instruments . 13
4.6.1 General . 13
4.6.2 Signal generator . 13
4.6.3 Filter . 15
4.6.4 Level meter . 16
4.6.5 Distortion meter . 17
4.6.6 Frequency meter . 18
4.6.7 Group delay meter . 18
4.6.8 Analogue spectrum analyzer . 19
4.6.9 Digital waveform monitor . 19
4.6.10 Voltage amplifier . 19
4.6.11 Standard digital player . 20
5 Methods of measurement (digital-in/analogue-out) . 20
5.1 General . 20
5.2 Input/output characteristics . 20
5.2.1 Maximum output amplitude . 20
5.2.2 Gain difference between channels and tracking error . 20
5.3 Frequency characteristics . 21
5.3.1 Frequency response . 21
5.3.2 Group delay (phase linearity) . 21
5.4 Noise characteristics . 21
5.4.1 Signal-to-noise ratio (idle channel noise) . 21
5.4.2 Dynamic range . 22
5.4.3 Out-of-band noise ratio . 22
5.4.4 Channel separation . 22
5.5 Distortion characteristics . 23
5.5.1 Level non-linearity . 23

5.5.2 Distortion and noise . 23
5.5.3 Intermodulation. 23
6 Methods of measurement (analogue-in/digital-out) . 23
6.1 General . 23
6.2 Input/output characteristics . 23
6.2.1 Analogue to digital level calibration . 23
6.2.2 Maximum allowable input amplitude. 24
6.2.3 Gain difference between channel and tracking error . 24
6.3 Frequency characteristics . 24
6.3.1 Frequency response . 24
6.3.2 Group delay . 25
6.4 Noise characteristics . 25
6.4.1 Signal-to-noise ratio (idle channel noise) . 25
6.4.2 Dynamic range . 25
6.4.3 Folded noise . 26
6.4.4 Cross-talk . 26
6.4.5 Channel separation . 26
6.5 Distortion characteristics . 26
6.5.1 Level non-linearity . 26
6.5.2 Distortion and noise . 27
6.5.3 Intermodulation. 27
Bibliography . 28

Figure 1 – Analogue test signal waveform . 14
Figure 2 – Digital test signal waveform . 14

Table 1 – Actual frequencies used in the measurement . 11
Table 2 – Impulse conditions and measuring range . 19

– 4 – IEC 61606-1:2009  IEC 2009
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
AUDIO AND AUDIOVISUAL EQUIPMENT –
DIGITAL AUDIO PARTS –
BASIC MEASUREMENT METHODS
OF AUDIO CHARACTERISTICS –
Part 1: General
FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote
international co-operation on all questions concerning standardization in the electrical and electronic fields. To
this end and in addition to other activities, IEC publishes International Standards, Technical Specifications,
Technical Reports, Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC
Publication(s)”). 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. IEC collaborates closely
with the International Organization for Standardization (ISO) in accordance with conditions determined by
agreement between the two organizations.
2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
consensus of opinion on the relevant subjects since each technical committee has representation from all
interested IEC National Committees.
3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC
Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any
misinterpretation by any end user.
4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications
transparently to the maximum extent possible in their national and regional publications. Any divergence
between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in
the latter.
5) IEC provides no marking procedure to indicate its approval and cannot be rendered responsible for any
equipment declared to be in conformity with an IEC Publication.
6) All users should ensure that they have the latest edition of this publication.
7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and
members of its technical committees and IEC National Committees for any personal injury, property damage or
other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and
expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC
Publications.
8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of
patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 61606-1 has been prepared by IEC technical committee 100:
Audio, video and multimedia systems and equipment.
This second edition cancels and replaces the first edition published in 2003. It constitutes a
technical revision.
The significant technical changes with respect to the first edition are the following:
• changed the period of preconditioning;
• add A weighting filter in measuring instruments;
• correct the wrong reference number;
• some inappropriate descriptions have been improved.

The text of this standard is based on the following documents:
FDIS Report on voting
100/1547/FDIS 100/1581/RVD
Full information on the voting for the approval of this standard can be found in the report on
voting indicated in the above table.
A list of all parts of the IEC 61606 series, under the general title Audio and audiovisual
equipment – Digital audio parts – Basic measurement methods of audio characteristics, can
be found on the IEC website.
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.
The committee has decided that the contents of this publication will remain unchanged until
the maintenance result date indicated on the IEC web site under "http://webstore.iec.ch" in
the data related to the specific publication. At this date, the publication will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
– 6 – IEC 61606-1:2009  IEC 2009
AUDIO AND AUDIOVISUAL EQUIPMENT –
DIGITAL AUDIO PARTS –
BASIC MEASUREMENT METHODS
OF AUDIO CHARACTERISTICS –
Part 1: General
1 Scope
This part of IEC 61606 is applicable to the basic methods of measurement of the audio
characteristics of the digital audio part of audio and audiovisual equipment for all of consumer
use, professional use and personal computer.
The common measuring conditions and methods, described in this standard, are used for the
measurement of the performance characteristics of equipment having an audio bandwidth
equal to approximately one-half of the sampling frequency of a system, where the audio
information is processed in the form of digital data. CD players, DAT recorders, digital
amplifiers, digital sound broadcast receivers and television broadcast receivers with digital
sound are examples.
This standard describes test methods for equipment which has digital input with analogue
output and analogue input with digital output. Future revisions of this standard will cover
digital-in/digital-out and analogue-in/analogue-out tests.
This standard does not apply to a lossy compression signal and also does not apply to power
amplifiers.
NOTE 1 A digital audio system having an analogue input and an analogue output with digital signal processing
may have different characteristics from those of a pure analogue audio system due to sampling of the audio signal
and performance of incorporated A/D and D/A converters. Measurement methods described in IEC 60268-3 may
not give correct results when applied to a digital system.
NOTE 2 The methods described are mostly based on sampling frequencies of 32 kHz and higher.
NOTE 3 For tests of those systems of digital-in – digital-out, and analogue-in – analogue-out tests, refer to
AES17.
NOTE 4 This standard is planned to harmonize with the first edition of IEC 61606 (1997) , AES17 and EIAJ CP-
2i50.
2 Normative references
The following referenced documents are indispensable for the application of this document.
For dated references, only the edition cited applies. For undated references, the latest edition
of the referenced document (including any amendments) applies.
IEC 60038, IEC standard voltages
IEC 60107-5, Recommended methods of measurement on receivers for television broadcast
transmissions – Part 5: Electrical measurements on multichannel sound television receivers
using the NICAM two-channel digital sound system
—————————
IEC 61606:1997, Audio and audiovisual equipment – Digital audio parts – Basic methods of measurement of
audio characteristics (this publication has been replaced by the IEC 61606 series)

IEC 60268-2, Sound system equipment – Part 2: Explanation of general terms and
calculation methods
IEC 60268-3, Sound system equipment – Part 3: Amplifiers
IEC 60958 (all parts), Digital audio interface
IEC 61606-2, Audio and audiovisual equipment – Digital audio parts – Basic measurement
methods of audio characteristics – Part 1: Consumer use
IEC 61606-3, Audio and audiovisual equipment – Digital audio parts – Basic measurement
methods of audio characteristics – Part 3: Professional use
IEC 61606-4, Audio and audiovisual equipment – Digital audio parts – Basic measurement
methods of audio characteristics – Part 4: Personal computer
IEC 61079-4, Methods of measurement on receivers for satellite broadcast transmissions in
the 12 GHz band – Part 4: Electrical measurements on sound/data decoder units for the
digital subcarrier NTSC system
IEC 61079-5, Methods of measurement on receivers for satellite broadcast transmissions in
the 12 GHz band – Part 5: Electrical measurements on decoder units for MAC/packet systems
IEC 61672-1, Electroacoustics – Sound level meters – Part 1: Specifications
IEC 61883-6, Consumer audio/video equipment – Digital interface – Part 6: Audio and music
data transmission protocol
ITU-R BS 468-4, Measurement of audio-frequency noise voltage level in sound broadcasting
AES17, AES standard method for digital audio engineering – Measurement of digital audio
equipment
3 Terms, definitions, explanations and rated values
3.1 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1.1
aliasing components
output frequency components below the folding frequency made from the input signal above
the folding frequency
3.1.2
analogue full-scale amplitude
nominal signal level at the analogue input of an EUT corresponding to the digital full-scale
level
3.1.3
coding format
series of data bit stream with control information in accordance with the standard for which
the EUT is designed, such as IEC 60958, IEC 61883-6 or some kind of AV interface
NOTE A coding word is arranged as a 2’s complimentary binary form in this standard.

– 8 – IEC 61606-1:2009  IEC 2009
3.1.4
digital audio signal
series of digital signals expressed by sampled data
NOTE This data is constructed with LPCM (Linear Pulse Code Modulation) data.
3.1.5
digital interface for measurement
type of input or output digital interface which is used for measurement, such as IEC 60958,
IEC 61883-6 or some kind of AV interface
NOTE Details are defined in IEC 61606-2 (consumer use) or IEC 61606-3 (professional use).
3.1.6
digital signal generator
all types of digital generators, which including digital sine signal generators or package media
or RF signal generators
3.1.7
digital zero
signal that has a value consisting of all zeroes for all samples
3.1.8
equipment under test
EUT
equipment to be measured using the methods described in this standard
3.1.9
folding frequency
one half the sampling frequency of the digital system
NOTE Signals applied to the input with frequency components higher than this frequency are subject to aliasing.
3.1.10
full-scale level
FS
signal level of a sine wave whose positive peak value reaches the positive digital full scale,
leaving the negative maximum code unused
EXAMPLE The largest positive value is 7FFFH and the largest negative value is 8001H in 16 bit data.
3.1.11
in-band frequency range
frequency range from 4 Hz to upper band-edge frequency (see 3.1.19).
3.1.12
jitter
deviation of the timing of the transitions of a clock signal from their ideal or nominal times
3.1.13
normal load impedance
impedance which is connected to output terminals of EUT
NOTE The concrete value is defined in IEC 61606-2 (consumer use) or IEC 61606-3 (professional use) or
IEC 61606-4 (PC use).
3.1.14
normal measuring level
signal level equal to –20 dB
FS
3.1.15
normal source impedance
impedance which is connected to input terminals of EUT
NOTE The concrete value is defined in IEC 61606-2 (consumer use) or IEC 61606-3 (professional use)
IEC 61606-4 (PC use).
3.1.16
out-of-band frequencies
frequency range from folding frequency to 500 kHz.
NOTE Signals applied to the input in this frequency range are subject to aliasing.
3.1.17
sampling frequency
f
s
number of samples of a signal taken per unit time
3.1.18
signal level
dB
FS
result obtained from the following equation:
signal level (dB ) = 20 log (A/B)
FS 10
where A is the r.m.s. value of the signal whose level is to be determined, and B is the r.m.s.
value of a sine wave which corresponds to full-scale level in digital data or to analogue full-
scale level in analogue signals
3.1.19
upper band-edge frequency
frequency calculated by the equation:
f × 0,46
s
NOTE If f is higher than 44,1 kHz, the manufacturer may define the upper band-edge frequency between 20 kHz
s
and f × 0,46. In this case, the upper band-edge frequency should be stated in the system description by the
s
manufacturer.
3.1.20
word length
number of bits of a data element
NOTE The least significant bit of the data element should not be ignored.
3.2 Explanation of term “jitter”
The performance of conversion processes are potentially affected by jitter present on the
synchronization input, the digital audio inputs, or both. For example, if the sampling clock for
the analogue-to-digital converter inside the EUT is derived from or locked to either the
synchronization input or a digital audio input, jitter present on that input can degrade
conversion accuracy.
There are various types of jitter susceptibility to be considered such as analogue-to-digital
jitter susceptibility, digital-to-analogue susceptibility, and digital-to-digital susceptibility. See
AES17 for detailed discussion on the subject.

– 10 – IEC 61606-1:2009  IEC 2009
3.3 Rated values
For a full explanation of these terms, see IEC 60268-2. The following are rated conditions for
digital audio equipment and should be specified by the manufacturer:
• rated supply voltage;
• rated supply frequency;
• rated pre-emphasis and de-emphasis characteristics;
• rated digital input word length;
• rated sampling frequencies.
4 Measuring conditions
4.1 Environmental conditions
Air pressure 96 kPa ± 10 kPa
Ambient temperature 15 °C to 35 °C
Relative humidity
60 % ± 15 %
4.2 Power supply
4.2.1 Supply voltage
The rated power supply voltage, as specified in IEC 60038, shall be used. The tolerance of
the supply voltage should be ±1 % or less. A tolerance of up to ±10 % may be allowed if the
results of the measurements are not noticeably affected.
4.2.2 Frequency(ies)
The power supply frequency(ies) specified by the manufacturer shall be used. The tolerance
of the frequency should be ±2 % or less. A d.c. power supply may be used if specified.
4.2.3 High-frequency and harmonic components (or ripples) in the power supply
output
High-frequency components in the power supply output should be less than the level which
affects the result of measurement.
4.3 Test signal frequencies
The frequency of the test signal shall be selected from the actual values in Table 1. In
catalogues and other documents, where precision is not required or implied in the description,
it is permitted to use the normal figures shown in Table 1. Unless otherwise specified, the
reference frequency for measurements shall be 997 Hz, which may be stated in non-critical
contexts, as 1 kHz.
Table 1 – Actual frequencies used in the measurement
Actual frequency
Nominal
Hz
Hz
f = f = f = f = f = f = f =
s s s s s s s
32 kHz 44,1 kHz 48 kHz 88,2 kHz 96 kHz 176,4 kHz 192 kHz
4 4 4 4 4 4 4 4
8 7 7 7 7 7 7 7
16 17 17 17 17 17 17 17
32 31 31 31 31 31 31 31
63 61 61 61 61 61 61 61
125 127 127 127 127 127 127 127
250 251 251 251 251 251 251 251
500 499 499 499 499 499 499 499
1 000 997 997 997 997 997 997 997
2 000 1 999 1 999 1 999 1 999 1 999 1 999 1 999
4 000 3 997 3 997 3 997 3 997 3 997 3 997 3 997
8 000 7 993 7 993 7 993 7 993 7 993 7 993 7 993
10 000 10 007 10 007 10 007 10 007 10 007 10 007 10 007
12 000 12 503 - - - - - -
14 000 13 999 - - - - - -
14 500 14 501 - - - - - -
16 000 - 16 001 16 001 16 001 16 001 16 001 16 001
18 000 - 17 997 17 997 - - - -
20 000 - 19 997 19 997 19 997 19 997 19 997 19 997
22 000 - - 22 001 - - - -
30 000 - - - 30 011 30 011 - -
35 000 - - - 34 981 34 981 - -
40 000 - - - 40 009 40 009 40 009 40 009
44 000 - - - - 43 997 - -
50 000 - - - - - 49 999 49 999
70 000 - - - - - 70 001 70 001
80 000 - - - - - 79 999 79 999
88 000 - - - - - - 88 001
If a sweep signal is used in the measurement, the sweep frequency range is from 16 Hz to
1/2 × f .
s
4.4 Standard setting
4.4.1 Standard input conditions for the EUT
4.4.1.1 Analogue input
Connect the EUT with the source equipment which has normal source impedance.
4.4.1.2 Digital input
Connect the EUT to the digital interface, for which the EUT is designed.

– 12 – IEC 61606-1:2009  IEC 2009
4.4.1.3 RF input
See IEC 60107-5, IEC 61079-4 and IEC 61079-5.
4.4.2 Standard output conditions for the EUT
4.4.2.1 Analogue output
Analogue output terminals which are connected to subsequent equipment shall be terminated
with the normal load impedance.
4.4.2.2 Digital output
Digital audio output terminals shall be terminated in a manner appropriate to the output
interface format.
4.4.3 Standard setting of controls
The following settings apply.
a) Each channel of the EUT is set to the standard input and output conditions.
b) Setting of level controls
For analogue-in/digital-out devices:
When a sinusoidal input signal of 997 Hz and the normal measurement level is applied to
the input terminals of the EUT, adjust the level control so as to obtain the normal
measurement level across the digital output. If the EUT has no digital output terminal and
it only records the data to recording media, adjust the level control so as to record the
normal measurement level into the recording media.
For digital-in/analogue-out devices:
When a sinusoidal signal of 997 Hz and the normal measurement level is applied to the
digital input terminal of the EUT, adjust the level control so as to obtain an analogue
output signal at the normal measurement level across the analogue output terminals with a
normal load impedance.
The level control shall be set to the maximum position if the output level cannot come to
the normal measurement level.
c) If the EUT is equipped with a balance control, it shall be set to the centre position.
d) Setting of the pre-emphasis and de-emphasis:
If pre-emphasis and/or de-emphasis are optional then they shall be turned off, if possible.
If results with pre-emphasis or de-emphasis are required for the measurement, these shall
be stated separately and the emphasis characteristics used shall be stated with the results.
e) Setting of other controls:
The tone controls, inter-channel balance controls and others shall be set to the positions
specified by the manufacturer, so that the EUT has a flat frequency response. The
loudness control and the filters shall be turned off, if possible. If this is not possible, this
shall be stated with the results. The condition of any other controls that can affect the
audio signal shall be stated with the result.
4.5 Preconditioning
The equipment shall be connected under normal operating conditions for the manufacturer-
specified preconditioning period prior to any measurements being performed. This condition is
intended to allow the equipment to stabilize. If no preconditioning period is specified by the
manufacturer, an one hour period shall be assumed. Should operational requirements
preclude preconditioning, the manufacturer shall state so.
Should power to the equipment be interrupted during the measurement, sufficient time shall
be allowed for restabilization to be realized.

4.6 Measuring instruments
4.6.1 General
All of analogue measuring instruments are applicable up to a 20 bit system because the
lowest signal level of a 24 bit system such as quantization noise is lower than thermal noise
which is caused by input impedance of analogue measuring instruments.
Definitions given in this standard are elementary functions of measuring instruments.
Then these definitions can be applied not only to a discrete measuring instrument but also to
a combined measuring instrument.
If input impedance of instruments which are ready to use don’t conform to the definition of this
clause, a register may be used to connect across the input terminals to get the right value.
4.6.2 Signal generator
4.6.2.1 Single sine wave generator
4.6.2.1.1 Analogue signal generator
Output impedance: normal source impedance
Frequency error: less than ±2 %
Output signal level: up to 3 dB over the analogue full-scale amplitude
Distortion: distortion of the signal generator shall be less than a level which does
not affect the performance of EUT
4.6.2.1.2 Digital sine signal generator
The digital signal generator shall be able to supply coding format of digital audio signal. A
signal is calculated from ideal sine wave form.
Output interface format: digital interface for measurement
Frequency error: error is less than 1/f
s
Output signal level: from zero level to full-scale level
Error accuracy: better than 1/2 LSB
4.6.2.2 Signal generator for inter-modulation measurement
A generator for inter-modulation measurement shall generate the two-tone signal, composed
of 60 Hz (or 70 Hz) and 7 kHz mixed at a ratio of 4:1.
In the case of digital signal generator, the peak level of the signal is the same as the peak
level of full-scale level.
In the case of analogue signal generator, the peak level of the signal is the same as analogue
full scale amplitude.
It is desirable that the test signal for CCIF inter-modulation test (11 kHz + 12 kHz) is also
available from the generator.
– 14 – IEC 61606-1:2009  IEC 2009
4.6.2.3 Signal generator for group delay measurement
4.6.2.3.1 Analogue signal
The analogue signal generator for group delay measurement shall generate a test signal with
the waveform of Figure 1.
1,41 V r.m.s.
0,707 V r.m.s.
0  V r.m.s.
T
NOTE
T = 1/f
1 s
IEC  1215/09
Figure 1 – Analogue test signal waveform

Output impedance: normal source impedance.
Normally, the repetition rate of the signal is 4 Hz. But if an input signal level does not satisfy
the level at which an analogue group delay meter can work correctly, a repetition rate as
given in Table 2 may be used.
4.6.2.3.2 Digital signal
The digital signal generator for group delay measurement for digital interface, packaged
media and digital broadcast, shall generate a test signal with the waveform of Figure 2.

4 000 H
2 000 H
0 000 H
T
NOTE
T = 1/f IEC  1216/09
1 s
Figure 2 – Digital test signal waveform
Normally, the repetition rate of the signal is 4 Hz. But if an input signal level does not satisfy
the level at which a digital group delay meter can work correctly, a repetition rate as given in
Table 2 may be used.
This digital group delay meter should synchronously have analogue output, having the same
waveform as the digital data waveform.
4.6.2.4 Packaged media for testing
A digital packaged medium may be used when it generates signals which are consistent with
the digital sine signal generator, the signal generator for inter-modulation measurement or the
signal generator for group delay measurement.

4.6.2.5 RF signal generator
An RF signal generator may be used when a modulated output data is consistent with the
digital sine signal generator, the signal generator for inter-modulation measurement or the
signal generator for group delay measurement.
4.6.3 Filter
4.6.3.1 Low pass filter (analogue)
Input impedance: normal load impedance
Output impedance: normal source impedance
Transmission distortion: no effect shall be observed to the measured values
4.6.3.2 Band pass characteristics
Pass band 4 Hz to upper band-edge frequency
Ripple: less than ±0,3 dB
Stop band 0,55 f and above
s
Attenuation: more than 60 dB
If upper band-edge frequency is not 0,46 f then the stop band is upper band-
s
,
edge frequency + f × 1/10 and above
s
4.6.3.3 Out-of-band filter (analogue)
Input impedance: normal load impedance
Output impedance: normal source impedance
Transmission distortion: no effect shall be observed to the measured value.
Band pass characteristics
Pass band:
Frequency range: Upper band-edge frequency + (1/10 × f ) to 500 kHz
s
Ripple: less than ± 0,3 dB
Lower stop frequency
Frequency range: below the upper band-edge frequency
Attenuation: more than 60 dB
Upper stop frequency
Frequency range: above 500 kHz
Attenuation: more than 18 dB/octave

– 16 – IEC 61606-1:2009  IEC 2009
4.6.3.4 Narrow band-pass filter (analogue and digital)
4.6.3.4.1 Input/output characteristics
For analogue signal
a) Input impedance: normal load impedance
b) Output impedance: normal source impedance
For digital signal
Applicable to digital interface for measurement.
4.6.3.4.2 Transmission distortion
No effect shall be observed to the measured values.
4.6.3.4.3 Transmission characteristics
Pass band: ripple: less than ±0,3 dB at measuring frequency.
Stop band: attenuation: more than −60 dB at half and twice the measuring frequencies.
4.6.3.4.4 Centre frequency of the filter
The centre frequencies of the narrow band pass filter shall comply with Table 1.
4.6.3.5 Weighting filter
Two types of weighting filter may be used.
One is the weighting filter which shall comply with ITU-R BS 468-4.
Another weighing filter used shall have A-weighing characteristics with tolerances less than
1 dB as specified for sound level measurements in IEC 61672-1.
The selection of the filter shall be defined in the corresponding methods.
4.6.4 Level meter
4.6.4.1 Digital level meter
A digital level meter shows the r.m.s. level as dB .
FS
Frequency range: in-band frequency range
NOTE All of the frequency range may be used if the calculation data is not affected.
Measuring range: FS to 1 LSB
Error: less than 1 % of reading or 1/2 LSB. The larger value is applied.
Input interface format: Applicable to digital interface for measurement.
Details: The details are defined in IEC 61606-2 (consumer use) or
IEC 61606-3 (professional use) or IEC 61606-4 (PC use), as
appropriate.
4.6.4.2 Analogue in-band level meter
The analogue in-band level meter indicates the r.m.s. value of a sinusoidal signal.
Frequency range: from 4 Hz to upper band-edge frequency
Input impedance: in the case of measuring EUT output directly: Normal load impedance,
other cases: 100 kΩ or more
Measuring range: +30 dB to –115 dB (0 dB = 1 V r.m.s.)
Error: less than 2 % of a full-scale value in the frequency range
NOTE If the analogue in-band level meter has not sufficient sensitivity, a voltage amplifier may be added before
the analogue in-band level meter.
4.6.4.3 Analogue out-of-band level meter
The analogue out-of-band level meter indicates the r.m.s. value of a sinusoidal signal.
Frequency range: from upper band-edge frequency to 500 kHz
Input impedance: normal load impedance
Error: error is less than 2 % of a full-scale value in the frequency range
Measuring range: 0 dB to –100 dB ( 0 dB = 1 V r.m.s.)
4.6.5 Distortion meter
4.6.5.1 Analogue distortion meter
A distortion meter shall be capable of measuring the harmonics and noise after removing the
fundamental frequency component. The measured data shall be indicated in % which is a
r.m.s. value ratio of harmonics and noise to total signals.
Input impedance: normal load impedance
Error: less than ± 3 % of full scale value of the measuring range
NOTE If the analogue distortion meter has not sufficient sensitivity, a voltage amplifier may be added before the
analogue in-band level meter.
4.6.5.2 Digital distortion meter
4.6.5.2.1 General
Calculate a ratio of the total signal output to the noise and distortion component. They are
calculated as an r.m.s. value. The result is shown in %.
4.6.5.2.2 Specifications
Input interface format: applicable to digital interface for measurement.
Frequency range: signal components are calculated from 4 Hz to the upper band-
edge frequency
– 18 – IEC 61606-1:2009  IEC 2009
Measuring signal level: 2 bits below FS to 1 LSB.
Error: less than 3 % of the reading or 1 LSB. The larger value is
applied.
4.6.5.2.3 Details
The details are defined in IEC 61606-2 (consumer use) or IEC 61606-3 (professional use) or
IEC 61606-4 (PC use), as appropriate.
4.6.6 Frequency meter
The tolerance of frequency is less than 1 %.
4.6.7 Group delay meter
4.6.7.1 General
If input data is an analogue signal, it is converted to digital data whose accuracy should be
better than 16 bits.
4.6.7.2 Calculation of delay time
The delay time of 997 Hz is calculated by the phase delay Φ ° which is calculated at 997 Hz
R
by Fourier transformation. This delay time τ is calculated by the following equation.
R
τ = (–Φ °/360) × (1/997)
R R
The delay time of the measurement frequency is calculated by the phase delay Φ ° which is
R
calculated at measurement frequency by Fourier transformation. This delay time τ is
C
calculated by the following equation.
τ = (–Φ °/360) × (1/f)
C C
Digital group delay τ is calculat
...