CIRCULAR

Issuing the "National Technical Regulation on Electromagnetic Compatibility for Cordless Audio Devices Operating at Frequencies from 25 MHz to 2000 MHz"

Pursuant to the Law on Standards and Technical Regulations dated June 29, 2006;

Pursuant to the Law on Telecommunications dated November 23, 2009;

WHEREAS, the Law on Radio Frequency Spectrum dated November 23, 2009;

WHEREAS, Decree No. 127/2007/NĐ-CP dated August 1, 2007 of the Government detailing and guiding the implementation of certain provisions of the Law on Technical Standards and Regulations;

Pursuant to Decree No. 78/2018/NĐ-CP dated May 16, 2018 of the Government amending and supplementing certain articles of Decree No. 127/2007/NĐ-CP dated August 1, 2007 of the Government detailing the implementation of certain provisions of the Law on Standards and Technical Regulations;

Pursuant to Decree No. 48/2022/NĐ-CP dated July 26, 2022 of the Government stipulating the functions, tasks, powers, and organizational structure of the Ministry of Information and Communications;

Pursuant to the proposal of the Director of the Science and Technology Department,

The Minister of Information and Communications issues this Circular stipulating the National Technical Regulation on Electromagnetic Compatibility for Cordless Audio Devices Operating at Frequencies from 25 MHz to 2000 MHz.

Article 1. Attached herewith is the National Technical Regulation on Electromagnetic Compatibility for Cordless Audio Devices Operating at Frequencies from 25 MHz to 2000 MHz (QCVN 130:2022/BTTTT).

Article 2. This Circular takes effect from July 1, 2023.

Article 3. The Heads of the Office, Department of Science and Technology, Heads of agencies and units under the Ministry of Information and Communications, Directors of Provincial Departments of Information and Communications, and relevant organizations and individuals are responsible for implementing this Circular.

 

 

 

 

 

 

 

 

 

SOCIALIST REPUBLIC OF VIET NAM

 

 

 

QCVN 130:2022/BTTTT

 

 

AMENDMENT 1:2025 QCVN 07:2023/BXD

ON ELECTROMAGNETIC COMPATIBILITY FOR CORDLESS AUDIO DEVICES OPERATING AT FREQUENCIES FROM 25 MHz TO 2000 MHz

 

National technical regulation

on electromagnetic compatibility for cordless audio devices

operating on frequencies between 25 MHz and 2000 MHz

 

 

 

 

 

 

 

 

 

 

 

 

 

HANOI - 2022

 

Table of Contents

 

1. GENERAL PROVISIONS

1.1 SCOPE

1.2 APPLICABLE OBJECTS

1.3 REFERENCED DOCUMENTS

1.4 DEFINITIONS OF TERMS

1.5 ABBREVIATIONS

2 TECHNICAL REQUIREMENTS

2.1 EMISSIONS

2.2 IMMUNITY

2.3 TECHNICAL CONDITIONS

2.3.1 ENVIRONMENTAL CONDITIONS

2.3.2 MEASUREMENT CONDITIONS

2.3.3 SIGNAL STIMULUS ARRANGEMENT

2.3.4 EXCLUDED BANDWIDTH

2.3.5 RECEIVER NARROW BAND RESPONSE

2.3.6 NORMAL MODULATION TESTING

2.4 AUXILIARY EQUIPMENT

2.5 QUALITY CRITERIA

2.5.1 INTRODUCTION

2.5.2 QUALITY REQUIREMENTS

3 MANAGEMENT PROVISIONS

4 RESPONSIBILITIES OF ORGANIZATIONS AND INDIVIDUALS

5 IMPLEMENTATION ORGANIZATION

ANNEX A (REGULATION) Harmonized System (HS) Code for Cordless Audio Devices Operating at Frequencies from 25 MHz to 2000 MHz

ANNEX B (REGULATION) Sound Stimulation of Wireless Microphones, Measurement Setup Conditions and Configuration

ANNEX C (REFERENCE) Examples of Cordless Audio Devices within the Scope of the Regulation

LIST OF REFERENCE DOCUMENTS

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Foreword

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

AMENDMENT 1:2025 QCVN 07:2023/BXD

 

ON ELECTROMAGNETIC COMPATIBILITY FOR CORDLESS AUDIO DEVICES OPERATING AT FREQUENCIES FROM 25 MHz TO 2000 MHz

 

National technical regulation

on electromagnetic compatibility for cordless audio devices

operating on frequencies between 25 MHz and 2000 MHz

 

1. GENERAL PROVISIONS

1.1 SCOPE

This regulation sets out the requirements for electromagnetic compatibility (EMC) for cordless audio devices operating at frequencies from 25 MHz to 2000 MHz.

This regulation specifies the EMC measurements, testing methods, limits, and quality criteria for cordless audio devices. These devices may use analog or digital modulation techniques.

Examples of such devices are provided in Annex C of this regulation.

Other transmitters or receivers used in conjunction with cordless audio devices are not within the scope of this regulation.

In case of discrepancies (such as special testing conditions, concepts, terms) between this regulation and regulation QCVN 18:2022/BTTTT, the provisions of this regulation shall apply.

Environmental classification, emission, and immunity requirements in QCVN 18:2022/BTTTT shall be applied except for special conditions specified in this regulation.

Technical specifications related to antenna ports and emissions from device enclosures are not within the scope of this regulation but will be regulated in corresponding product standards and regulations to effectively utilize radio frequency spectrum.

The Harmonized System (HS) codes for devices within the scope of this regulation are specified in Annex A.

The operating frequencies of cordless audio devices must comply with the management and usage regulations for radio frequencies in Vietnam.

1.2 APPLICABLE OBJECTS

This regulation applies to domestic and foreign organizations and individuals engaged in the production and business of devices within the scope of this regulation in Vietnam.

1.3 REFERENCED DOCUMENTS

QCVN 18:2022/BTTTT, National Technical Regulation on Electromagnetic Compatibility for Wireless Telecommunication Equipment.

QCVN 91:2015/BTTTT, National Technical Regulation on Cordless Audio Devices Operating at Frequencies from 25 MHz to 2000 MHz.

ETSI EN 300 422-1 (V2.1.2) (01-2017): "Wireless Microphones; Audio PMSE up to 3 GHz; Part 1: Class A Receivers; Harmonised Standard covering the essential requirements of Article 3.2 of Directive 2014/53/EU".

ETSI EN 300 454-1 (V1.1.2) (08-2000): "Electromagnetic Compatibility and Radio Spectrum Matters (ERM); Wide Band Audio Links; Part 1: Technical Characteristics and Test Methods".

ETSI EN 300 220-1 (V3.1.1) (02-2017): "Short Range Devices (SRD) Operating in the Frequency Range 25 MHz to 1000 MHz; Part 1: Technical Characteristics and Methods of Measurement".

1.4 DEFINITIONS OF TERMS

Terms defined in QCVN 18:2022/BTTTT and the following terms shall be used:

1.4.1 Cordless Audio Devices (cordless audio devices)

Radio frequency wave equipment used for short-range sound transmission. Typical examples of wireless audio devices include wireless microphones, wireless speakers (with radio transmission capability), wireless headphones, and wireless combined microphones/speakers.

1.4.2.Companding - decompression

The signal processing method for audio includes compressing the dynamic range of the audio before transmission and decompressing the signal at the receiver.

NOTE: This method is used to improve the performance of audio transmission over radio channels.

1.4.3.Integral Antenna

An antenna designed to be connected to the device without using standard connectors and considered part of the device.

NOTE: Integral antennas may be mounted inside or outside the device.

1.4.4.Switching Range

The largest frequency band within which the transmitter and receiver can operate without reprogramming or rearranging frequencies.

1.5.Abbreviations

2.TECHNICAL REQUIREMENTS

2.1.Transmission

Apply Table 1, Section 2.1.1 of QCVN 18:2022/BTTTT, including the ability to apply EMC emission measurement methods to relevant ports of the radio equipment and/or auxiliary equipment.

Specific conditions are defined in Table 1 related to the emission measurement method used in Section 2.1 of QCVN 18:2022/BTTTT.

Table 1 - Specific Conditions for EMC Emission Measurements

2.2.Immunity

Apply Section 2.2 of QCVN 18:2022/BTTTT, including the ability to apply EMC immunity measurement methods to relevant ports of the radio equipment and/or auxiliary equipment.

Specific conditions are defined in Table 2 related to the immunity measurement method used in Section 2.2 of QCVN 18:2022/BTTTT.

Table 2 - Specific Conditions for EMC Immunity Testing

2.3.Technical Conditions

2.3.1.Environmental Conditions

Technical requirements in this standard apply under the environmental operating conditions published by the manufacturer. The EUT must comply with all technical requirements of this standard at all times when operating within the environmental conditions published by the manufacturer.

2.3.2.Testing Conditions

Apply the testing conditions specified in Appendix A of QCVN 18:2022/BTTTT. Other testing conditions applicable to wireless audio devices and auxiliary equipment are detailed in this standard.

For emission and immunity tests, test conditions, test setup, etc., are specified in Sections 2.3.2 to 2.3.6 of this standard.

For EMC tests, portable or handheld transmitters must be mounted on a non-conductive stand and kept at least 0.8 meters away from any conductive surfaces. The EUT and any other equipment required to be evaluated before, during, and after testing must be connected according to the typical configuration for normal operation.

If the EUT is provided with a detachable antenna, the EUT must be tested with the antenna installed according to the typical configuration for normal operation.

For immunity tests, if the device belongs to the permitted group, information connection may be established at the start of testing and maintained throughout the testing process.

Testing conditions include:

• The transmitter must operate at its usual maximum RF output power, modulated by an appropriate modulation signal (see 2.3.6.1);
• Individual receivers or receivers of transmitters operating in single-channel mode, the desired RF input signal fed into the receiver must be modulated by an appropriate modulation signal (see 2.3.6.2);
• For dual-channel transceivers, the desired RF input signal fed into the receiver must be modulated by an appropriate modulation signal (see 2.3.6.2). The transmitter must operate at its usual maximum RF output power, modulated by a test modulation signal fed into the transmitter from the output of the receiver (loopback mode);
• Digital modulation systems must use predefined interfaces to convert between analog and digital domains (and vice versa).

2.3.3.Test Signal Setup

2.3.3.1.General

Apply the provisions in A.2 of Appendix A of QCVN 18:2022/BTTTT.

2.3.3.2.Test Signal Setup at the Input of the Transmitter

Apply the provisions in A.2.2 of Appendix A of QCVN 18:2022/BTTTT with the following modifications.

For transmitters designed to operate from an integrated or separate microphone (see Figure 2), it is permissible to use an audio inserter to inject a normal test modulation signal (see Figure 3). The audio inserter may be supplied by the manufacturer.

For equipment that can use multiple types of microphones, the manufacturer must specify the type of microphone used in the system, such as dynamic, condenser, or electret microphones. The transmitter is tested at the most sensitive input level with the test microphone.

For equipment not designed for use with integrated or separate microphones, the electrical signal shall be fed into the most sensitive input point (see Figure 1) using the longest cable normally supplied by the manufacturer with the equipment.

The modulated signal used for testing shall be a single-tone sine wave at 1 kHz at the level published by the manufacturer until the audio modulation reaches 100%.

The manufacturer may provide a suitable receiver to accompany it and can be used to establish information connection. In this case, an appropriate attenuator may be used in the accompanying receiver's input, see details in Appendix B.

In the case of systems using digital audio inputs and outputs, the test signal must pass through an appropriate converter to convert analog signals to digital signals and vice versa. The manufacturer must provide detailed information about the interface and test converters used for the test.

2.3.3.3.Test Configuration at the Output of the Transmitter

Apply the provisions at A.2.3 of Appendix A of QCVN 18:2022/BTTTT.

2.3.3.4.Test Configuration at the Input of the Receiver

Apply the provisions at A.2.4 of Appendix A of QCVN 18:2022/BTTTT with the following modifications.

The desired RF input signal to the receiver is modulated by a corresponding signal that corresponds to 100% audio modulation (maximum channel load level). If a modulated RF input signal cannot be provided to the receiver, testing can be performed using an unmodulated desired RF input signal.

The manufacturer must publish the level and method of generating the desired RF input signal. The selected level must be set at a value greater than 60 dB above the receiver's threshold sensitivity. Other similar wireless microphone systems may determine different levels corresponding to the application. This level must be recorded in the test report.

The manufacturer must provide a suitable transmitter to accompany it and can be used to establish information connection. In this case, an appropriate attenuator may be used in the EUT if necessary.

 

 

 

 

Figure 1 - Test configuration for built-in antennas; transmitter operation - electrical input signal

 

Figure 2 - Test configuration for built-in antennas; transmitter operation - audio input signal

 

Figure 3 - Example of an audio combiner

 

NOTE: An RF signal generator accompanying the transmitter may be placed inside the test chamber if necessary.

Figure 4 - Test configuration for built-in antennas; receiver operation

2.3.3.5.Test Configuration at the Output of the Receiver

Apply the provisions at A.2.5 of Appendix A of QCVN 18:2022/BTTTT with the following modifications.

The audio frequency output signal from the receiver can be combined into an external SINAD measurement system outside the test chamber. The characteristics of the SINAD system must ensure that the upper -3 dB bandwidth of the detector is greater than 16 kHz and the measured flatness error between frequencies 40 Hz and 16 kHz does not exceed ±2 dB. Signal combining devices used for testing must be included in the test report.

In the case of systems using digital audio outputs, the manufacturer must determine an appropriate converter to convert digital signals to analog signals. The manufacturer must provide detailed information about the interface and test converters used for the test. The interfaces must ensure compliance with the technical requirements mentioned above.

2.3.3.6.Test Configuration for Receiver and Transmitter Together (as a System)

Apply the provisions at A.2.5 of Appendix A of QCVN 18:2022/BTTTT.

For digital modulation systems, the manufacturer must determine an appropriate converter to convert analog signals to digital signals and vice versa. The determination mentioned above must be included in the test report.

2.3.4.Exclusion Bandwidth

2.3.4.1.General

Apply A.3 of Appendix A of QCVN 18:2022/BTTTT.

2.3.4.2.Exclusion Bandwidth for Receivers and Receivers of Transceivers

The exclusion bandwidth for receivers and receivers of transceivers is a frequency band determined by the switching range announced by the manufacturer, expanded as follows:

1) Type 1 and Type 2 equipment (as defined in 2.5)

- The lower frequency limit of the exclusion bandwidth is the lower frequency limit of the switching range minus 5% of the center frequency value of the switching range.

- The upper frequency limit of the exclusion bandwidth is the upper frequency limit of the switching range plus 5% of the center frequency value of the switching range.

2) Type 3 equipment (as defined in 2.5)

- The lower frequency limit of the exclusion bandwidth is the lower frequency limit of the switching range minus 5% of the center frequency value of the switching range or minus 10 MHz, choose the appropriate value to have the lowest frequency.

- The upper frequency limit of the exclusion bandwidth is the upper frequency limit of the switching range plus 5% of the center frequency value of the switching range or plus 10 MHz, choose the appropriate value to have the highest frequency.

The manufacturer must announce the type of equipment in the product accompanying documentation and must provide information about the type of equipment to the laboratory.

2.3.4.3.Exclusion Bandwidth for Transmitters

The lower frequency limit of the exclusion bandwidth is the lower frequency limit of the switching range minus 5% of the center frequency value of the switching range.

The upper frequency limit of the exclusion bandwidth is the upper frequency limit of the switching range plus 5% of the center frequency value of the switching range.

2.3.5.Narrowband Response of the Receiver

The responses on the receiver, the receiving part of the transceiver (dual function) occurring during immunity testing at discrete frequencies are narrowband responses (false responses) determined by the following method.

If during testing, the RF immunity test signal (see 2.2.3 and 2.2.6 of QCVN 18:2022/BTTTT) causes non-compliance of the receiver with specific criteria (see Appendix C), this non-compliance must be determined according to narrowband response or wideband phenomenon. Therefore, the frequency of the test signal is increased by twice the nominal 6 dB bandwidth of the IF filter immediately before the receiver's modulator, or if appropriate, the bandwidth of the device used for operation as determined by the manufacturer. The test is repeated with the test signal frequency reduced by the same amount.

If the receiver complies with the specified criteria in one or both frequency deviation cases, the response is considered a narrowband response.

If the receiver still does not comply with the criteria specified in one or both frequency deviation cases, this may be due to a narrowband response corresponding to an unwanted signal at a different frequency. In this case, the procedure is repeated with the test signal frequency increased or decreased twice the reference bandwidth or half the reference bandwidth above.

If the receiver still does not comply with the criteria specified in one or both frequency deviation cases, the phenomenon is considered broadband and therefore the device fails the EMC test.

For immunity testing, narrowband responses must be disregarded.

The identification criteria for narrowband responses of the EUT are the observed level reductions of the SINAD level at the audio output being lower than the limit of the relevant category as specified in Table 4, see 2.5.2.

The nominal frequency deviation used for identifying narrowband responses must be twice the bandwidth of the receiver's IF filter immediately before the demodulator, according to the manufacturer's specifications, for the first part of the identification procedure, and 2.5 times the receiver bandwidth for the second part.

For digital systems, narrowband responses must be limited below three times the system's published bandwidth (B). See ETSI EN 300 422-1, ETSI EN 300 454-1 QCVN 91:2015/BTTTT.

2.3.6.Test Modulation Normal

2.3.6.1.Transmitter

The transmitter is modulated by a 1,000 Hz sine wave audio signal provided through a suitable audio combiner or shielded transmission cable (e.g., coaxial cable). The level of this audio signal must be adjusted to achieve 100% audio modulation (maximum channel loading) of the desired signal.

For digital modulation systems, the manufacturer must specify the method and modulation parameters and provide appropriate conversion equipment to allow testing equivalent to 100% audio modulation.

2.3.6.2.Receiver

The desired RF input signal of the receiver must be set at the operating frequency within the designed operating frequency range and modulated by a 1,000 Hz sine wave audio signal provided through an antenna measurement placed inside the measurement room (for receivers with built-in antennas) or a shielded transmission cable such as coaxial cable (for receivers without built-in antennas). The level of the modulated signal must be adjusted to achieve 100% audio modulation (maximum channel loading) of the desired RF input signal of the receiver.

For digital modulation systems, the manufacturer must specify the method and modulation parameters and provide appropriate conversion equipment to allow testing equivalent to 100% audio modulation.

2.4.Assistive Equipment

Apply Appendix B of QCVN 18:2022/BTTTT.

2.5.Quality Criteria

2.5.1.Introduction

2.5.1.1.General

Wireless microphone devices are divided into three categories, each with its own quality criteria:

• Category 1 devices include wireless microphones and accompanying auxiliary devices for professional applications;
• Category 2 devices include wireless microphones, wireless audio devices, in-ear monitoring devices, and accompanying auxiliary devices for home entertainment;
• Category 3 devices include wireless microphones, wireless audio devices, wireless headphones, and accompanying auxiliary devices for general purposes (wireless microphones that meet technical and operational requirements as specified, regardless of application or intended use).

User manuals must contain information on the intended use of the product, specifically stated as "Professional Applications" (Category 1), "Home Entertainment" (Category 2), or "General Purpose" (Category 3).

Establishing a connection at the start of testing, maintaining the connection, and evaluating recovered signals (such as output audio signals) are used as quality criteria to assess essential functions of the device during and after testing.

Quality criteria A, B, and C listed in Table 3 must be applied as follows:

• Quality criterion A applies to continuous interference immunity measurements;
• Quality criterion B applies to intermittent interference immunity measurements;
• Quality criterion C applies to power interruption and overvoltage measurements exceeding a defined time period.

2.5.1.2.Common Quality Criteria

Devices must meet the common quality criteria specified in Table 3 and specific quality criteria detailed in Sections 2.5.2.1, 2.5.2.2, and 2.5.2.3.

Table 3 - Common Quality Criteria

2.5.2.Quality Requirements

2.5.2.1.Criteria for Devices Capable of Continuous Information Connection

1. General

The establishment of information connection at the start of testing, maintaining the connection, and evaluating recoverable signals, such as audio signals, shall be used as quality criteria to ensure that the essential functions of transmitters and/or receivers are assessed during and after the testing process.

Equipment must meet the minimum quality criteria specified for the types of equipment mentioned in Sections 2.5.1.1 and 2.5.1.2.

1. Quality criteria for continuous phenomena apply to transmitters (TX) and receivers (RX).

The following quality criteria for continuous phenomena apply to transmitters (TX) and receivers (RX) or the receiver part of single or dual receivers (RX) to allow for continuous information connection:

• Prior to testing, it must be ensured that the EUT, when paired through measuring equipment and not subjected to EMC effects, can generate a SINAD level higher than the minimum limit set out in Table 4 by at least 3 dB.
• During each individual exposure in the test sequence, it must be ensured that the information connection is maintained by means provided by the manufacturer.
• At the end of the testing, the EUT must operate as intended without losing control functions or user data as declared by the manufacturer, and the information connection must be continuously maintained throughout the testing process.

During and after testing, the output audio signal must be monitored and evaluated. During testing, the SINAD of the output audio signal must not decrease below the relevant limit specified in Table 4. After testing, SINAD must return to the level recorded before testing and must not be lower than the relevant limit specified in Table 4.

Table 4 - Continuous Phenomena, Minimum Quality Criteria

In cases where the EUT is only a transmitter and operates in standby mode, the tests must be repeated while the EUT is in standby mode to ensure that unintended signal transmission does not occur.

For EUTs that are transceivers, during testing, the transmitter must not operate incorrectly.

1. Quality criteria for transient phenomena apply to transmitters (TT) and receivers (RR).

The following quality criteria for transient phenomena apply to transmitters (TT) and receivers (RR) or the receiver part of single or dual transceivers (RR) to allow for continuous information connection:

• Prior to testing, it must be ensured that the EUT, when paired through measuring equipment and not subjected to EMC effects, can generate a SINAD level higher than the minimum limit set out in Table 4 by at least 3 dB.
• At the end of each exposure in the test sequence, the EUT must operate without users noticing any loss of information connection.
• At the end of all tests, including the series of individual exposures, the EUT must operate as intended without losing control functions or user data as declared by the manufacturer, and the information connection must be continuously maintained throughout the testing process.

After testing, the output audio signal must be monitored and evaluated. After testing, SINAD must return to the level recorded before testing or must not be lower than the relevant limit specified in Table 4.

In cases where the EUT is only a transmitter and operates in standby mode, the tests must be repeated while the EUT is in standby mode to ensure that unintended signal transmission does not occur.

For EUTs that are transceivers, during testing, the transmitter must not operate incorrectly.

2.5.2.2.Quality criteria for equipment that does not provide continuous information connection

For equipment that does not provide continuous information connection, the manufacturer must publish technical specifications of the equipment for acceptable levels of quality or quality degradation during and/or after immunity testing and include them in the test report. This quality specification must be included in the documentation and product description. Technical specifications related to Section 2.4.3 must also be considered.

The quality criteria established by the manufacturer must provide the same level of immunity protection as stated in Section 2.5.1.

For continuous immunity testing, equipment that does not allow for continuous information connection and accessories expected to be tested individually must meet the following quality criteria:

• Quality criterion A for type 1 equipment;
• Quality criterion C for type 2 and type 3 equipment

as described in Table 3.

For transient immunity testing, equipment that does not allow for continuous information connection and accessories expected to be tested independently must meet quality criterion B as described in Table 3, except for immunity testing against voltage dips and interruptions (see Section 2.2.8 of QCVN 18:2022/BTTTT), where it must be clearly stated that maintaining information connection is not required and therefore quality criterion C specified in Table 3 does not apply.

2.5.2.3.Quality criteria for auxiliary equipment tested independently

If the equipment is tested independently, the manufacturer must publish technical specifications of the equipment for acceptable levels of functionality or functional degradation during and/or after immunity testing and include them in the test report. This functionality specification must be included in the documentation and product description. Technical specifications related to Section 2.4.3 must also be considered.

The quality criteria established by the manufacturer must provide the same level of immunity protection as stated in Section 2.5.1.

3.MANAGEMENT REGULATIONS

3.1. Wireless audio devices within the scope defined in 1.1 must comply with the provisions of this Standard.

3.2. Measuring instruments and equipment: Comply with current regulations.

4.RESPONSIBILITIES OF ORGANIZATIONS AND INDIVIDUALS

4.1. Organizations and individuals involved are responsible for implementing the conformity declaration requirements for wireless audio devices in the frequency range from 25 MHz to 2,000 MHz and are subject to inspection by state management agencies according to current regulations.

5.IMPLEMENTATION

5.1. The Telecommunications Administration and Provincial Departments of Information and Communications are responsible for organizing guidance and managing wireless audio devices in the frequency range from 25 MHz to 2,000 MHz according to this Standard.

5.2. In cases where the provisions set forth in this Standard are changed, supplemented, or replaced, they shall be implemented according to the new document.

5.3. During the implementation of this Standard, if any issues arise or difficulties occur, relevant organizations and individuals shall reflect them in writing to the Ministry of Information and Communications (Science and Technology Department) for guidance and resolution./.

 

 

ANNEX A

Product Name, Goods According to QCVN

HS code for wireless audio equipment

frequency range from 25 MHz to 2 000 MHz

 

 

Provisions on the HS Code of Terrestrial Mobile Radio Equipment and Terrestrial Radio Relay Equipment

Product Name, Goods According to QCVN

Sound stimulation of wireless microphones, conditions for measurement setup and configuration

B.1 General

This annex specifies the methods of sound stimulation of the Equipment Under Test (EUT) when performing the electromagnetic compatibility (EMC) measurements as set out in this standard, acknowledging the somewhat unusual behavior of wireless microphones compared to general radio equipment.

Wireless microphones vary significantly in sensitivity and directionality of the sound pickup.

When testing wireless microphones, it must be remembered that many products use different compression-decompression techniques.

If there are difficulties or uncertainties regarding the characteristics of the test sample, communication with the manufacturer should take place.

B.2 Sound Stimulation

One part of the EMC test series specified in this standard requires providing a sound stimulus signal to the microphone converter. This can be achieved by at least two methods:

1. Using an electro-acoustic resonator (to avoid distortion of the calibration field, this device must be non-metallic and placed outside the calibration zone); or
2. Using a sound transmission tube (rigid or flexible but with a solid acoustic wall made of non-conductive material and with a constant internal diameter along its length).

The directional converter must have sufficient bandwidth and amplification capability to fully stimulate the modulation of the EUT with sound pressure at the microphone. However, overloading must be avoided.

The directional converter must be placed sufficiently far from the EUT's microphone (which is typically a moving coil type) to avoid magnetic coupling between converters and distortion due to the measurement electromagnetic field.

Adapters or suitable devices may be used to couple the directional converter with the EUT's microphone converter. Mounting devices must be securely fixed during the measurement process.

When the converter is coupled to the EUT via a sound tube, bends in the tube must be avoided or minimized. Any bend in the tube must ensure a bending radius larger than the internal diameter of the tube.

Standing waves in the tube must be mitigated by placing cotton wool dampers spaced 150 mm apart along the length of the tube. The directional converter should be placed inside the measurement room to minimize the length of the tube.

NOTE: This method has been successfully tested using a 1-meter-long tube. The tube used was a 12.5 mm reinforced plastic pipe. The directional converter was a 75 mm car radio speaker with a large ferrite magnet capable of displacing the cone apex by more than 10 mm. The adapter was connected to the tube using a household plastic funnel.

Annex C

(For reference)

Examples of wireless audio equipment within the scope of this standard

C.1 Wireless Microphone Equipment

Wireless microphone equipment operates with continuous RF output signals and typically runs continuously for several hours. Signal modulation may be analog or digital. Transmitters usually operate at maximum RF output power levels up to 50 mW. Wireless microphones are used for professional purposes in theaters, performances, promotions, etc., and can be distinguished from voice communication devices (such as PMR) by the following operational characteristics:

• Wider audio bandwidth;
• Higher audio signal-to-noise ratio;
• Lower audio frequency distortion.

Assistive devices for people with disabilities, tour guide systems, in-ear monitoring devices, and similar RF equipment operate similarly to wireless microphones but with reduced variations in bandwidth and RF output power, which may degrade voice or speech signal transmission quality.

C.2 Other Wireless Audio Equipment

Wireless audio equipment includes wireless headphones and speakers. Transmitters may be installed in buildings, on transportation means, or on persons. The term "wireless" also describes infrared connections or wireless connections not using RF but in this standard, it only applies to RF wireless systems. Analog or digital audio equipment may be designed for channel bandwidths requiring 300 kHz, although multi-channel equipment such as surround sound systems may require higher bandwidths of 600 kHz or 1 200 kHz as described in QCVN 91:2015/BTTTT.

With this operational classification, the following applications may be identified (non-exhaustive list):

• Wireless Speakers: Wireless speakers are used in home environments and are used to wirelessly connect to sound systems or TVs and similar systems;
• Wireless Headphones: Wireless headphones are used in home environments and are used to wirelessly connect to sound systems or TVs and similar systems;
• In-Ear Monitoring Devices: In-ear monitoring devices are used by performers and recording studio personnel to receive personal performance return signals (monitoring). This helps adjust the performer's voice or mix multiple signal sources. Typically, these devices are stereo or surround sound audio equipment.

Bibliography

 

[1] ETSI EN 301 489-9 V2.1.1 (2019-04): ElectroMagnetic Compatibility (EMC) standard for radio equipment and services; Part 9: Specific conditions for wireless microphones, similar Radio Frequency (RF) audio link equipment, cordless audio and in-ear monitoring devices; Harmonised Standard covering the essential requirements of Article 3.1(b) of Directive 2014/53/EU;