GB 3241-1982Electroacoustics - Octave-band and fractional-octave-band filters - Part 1: Specifications (English PDF)

Foreword

This document is in accordance with the provisions of GB/T 1.1-2020 "Guidelines for standardization work Part 1: Structure and drafting rules for standardization documents" Drafting.

This document is part 1 of GB/T 3241 "Electroacoustic octave and fractional octave filters". GB/T 3241 has been published the following parts.

--- Part 1: Specification;

--- Part 2: Type evaluation test.

This document partially replaces the relevant terms and definitions, properties and specifications in GB/T 3241-2010 "Electroacoustic octave and fractional octave filters" Compared with the relevant contents of GB/T 3241-2010, in addition to structural adjustments and editorial changes, the main changes are.

The technical changes are as follows.

a) The scope of application has been changed (see 1.2, 1.2 of the 2010 edition);

b) The design objectives have been changed (see 1.3, 5.2, and 3.2 of the 2010 edition);

c) Changed the terms and definitions of "reference level range", "reference input signal level", "level linearity error" and "level range controller" (see 3.20, 3.21, 3.22, 3.24, 3.18, 3.19, 3.22, 3.24 of the 2010 edition);

d) The temperature and relative humidity in the reference environmental conditions have been changed (see Chapter 4, 4.13 of the 2010 edition);

e) Changed the acceptance limit of filter effective bandwidth deviation (see 5.12, 4.5 of the 2010 edition);

f) The linear operating range of the filter has been changed (see 5.13, 4.6 of the 2010 edition);

g) Deleted the contents of "real-time operation" and "flat frequency response" (see 4.7 and 4.10 of the 2010 edition);

h) Added the contents of "time-invariant operation", "overload indicator" and "filter decay time" (see 5.14, 5.17 and 5.18);

i) Changed the filter air temperature range, the temperature and relative humidity of the controllable working environment area (see 5.22.2, 2010 edition) 4.14.2).

This document is equivalent to IEC 61260-1:2014 "Electroacoustic octave and fractional octave filters Part 1: Specification".

Introduction

A filter is a device that separates the components of a signal by frequency, and octave and fractional octave filters are devices that have a single A bandpass filter with a transmission band and an upper cutoff frequency and a lower cutoff frequency ratio equal to an octave frequency ratio or a certain power thereof. Octave and fractional Octave filters are usually used in conjunction with sound measuring instruments such as sound level meters for spectral analysis of sound signals.

GB/T 3241 aims to specify the performance requirements for octave and fractional octave filters and to describe the type evaluation tests and periodic tests.

The method is planned to consist of three parts.

--- Part 1: Specification. The purpose is to specify the performance requirements for octave and fractional octave filters.

--- Part 2: Type evaluation test. The purpose is to ensure that all testing laboratories use a consistent method to perform octave and fractional Type evaluation test of octave band filters.

--- Part 3: Periodic test. The purpose is to ensure that all testing laboratories or metrology laboratories perform octave testing in a consistent manner.

and periodic experiments with fractional-octave filters.

To evaluate compliance with performance specifications, this document uses different criteria from GB/T 3241-2010.

GB/T 3241-2010 does not provide any requirements or recommendations for considering measurement uncertainty in the evaluation of conformity to performance specifications.

Due to the lack of requirements or recommendations on measurement uncertainty, when the measured deviation from the design target is close to the limit of the allowable deviation, the determination of compliance with the specification becomes ambiguous. If compliance is determined based on whether the measured deviation exceeds the limit, then the octave and the end user of the fractional-octave band filter will be subject to the risk that the actual deviation from the design target exceeds the limit.

To eliminate ambiguity, the 29th Technical Committee of the International Electrotechnical Commission (IEC) determined at its 1996 meeting that in formulating standards, Measurement uncertainty should be taken into account when evaluating the performance of the system.

This document adopts the modified criteria for compliance with the specification. Compliance is confirmed when the following conditions are met simultaneously.

a) the measured deviation from the design target does not exceed the applicable acceptance limit;

b) The measurement uncertainty does not exceed the corresponding maximum permissible uncertainty.

The acceptance limits are similar to the design and manufacturing tolerance limits in GB/T 3241-2010.

The actual measurement uncertainty and the maximum allowable measurement uncertainty are determined based on a coverage probability of 95%, unless there is more specific information.

Otherwise, the acceptance limits and maximum allowable uncertainties specified in this document can be used to evaluate specific octave or fractional octave filters.

or the contribution of the filter bank to the total measurement uncertainty.

Electroacoustic Octave and Fractional Octave Filters Part 1: Specification

1 Scope

1.1 This document specifies the performance requirements for bandpass filters implemented using analog, sampled data, and digital methods.

There are filters whose relative attenuation characteristics have a passband region that is a constant percentage of the exact center frequency.

The instrument may contain any number of adjacent bandpass filters covering any desired frequency range.

1.2 This document gives the performance requirements for two filter grades, Class 1 and Class 2.In general, the specifications for Class 1 and Class 2 filters have similar characteristics.

The main differences are the acceptance limits and the operating temperature range. The acceptance limits of Class 2 are greater than or equal to the acceptance limits of Class 1.

The maximum permissible expanded measurement uncertainty is determined.

1.3 The design performance requirements given are based on octave ratios and center frequencies to the base 10.

1.4 Bandpass filters meeting the performance requirements of this document may be part of various measurement systems or a component such as a spectrum analyser.

A component part of a specific instrument.

1.5 This document specifies the range of environmental conditions under which filters may be operated. The required range depends on whether the instrument incorporating the filter is designed to operate in an environment that is Controlled environmental conditions or more general on-site work.

1.6 Bandpass filters meeting the requirements of this document are suitable for various signals, such as time-varying, intermittent or steady-state, broadband or discrete frequency.

It can provide frequency band filtered spectral information for signals of long or short duration.

2 Normative references

The contents of the following documents constitute essential clauses of this document through normative references in this document.

For referenced documents without a date, only the version corresponding to that date applies to this document; for referenced documents without a date, the latest version (including all amendments) applies to this document.

GB/T 9254.1-2021 Electromagnetic compatibility of information technology equipment, multimedia equipment and receivers Part 1: Emission requirements (CISPR32.2015,MOD) Note. There is no technical difference between the content cited in GB/T 9254.1-2021 and the content cited in CISPR22.2008.

GB/T 17626.3-2023 Electromagnetic compatibility test and measurement technology Part 3: Radio frequency electromagnetic field radiation immunity test (IEC 61000-4-3:2020,IDT) Note. There is no technical difference between the referenced content of GB/T 177626.3-2023 and the referenced content of IEC 61000-4-3:2006.

GB/T 17799.1-2017 General standard for electromagnetic compatibility - Immunity for residential, commercial and light industrial environments (IEC 61000-6-1:2005,MOD) Note. There is no technical difference between the referenced content of GB/T 17799.1-2017 and the referenced content of IEC 61000-6-1:2005.

GB/T 17799.2-2023 General electromagnetic compatibility standards Part 2: Immunity standards for industrial environments (IEC 61000-6-2:2016,MOD) Note. There is no technical difference between the referenced content of GB/T 17799.2-2023 and the referenced content of IEC 61000-6-2:2005.

GB/T 17799.3-2023 General standard for electromagnetic compatibility Part 3: Emissions of equipment in residential environments (IEC 61000-6-3.

2020, IDT)

Note. There is no technical difference between the referenced content of GB/T 17799.3-2023 and the referenced content of IEC 61000-6-3:2006.

ISO/IEC Guide 98-3 Measurement uncertainty Part 3: Guide to the expression of uncertainty in measurement (GUM..1995)