GB/T 7584.2-2026Acoustics - Hearing protectors - Part 2: Estimation of effective A-weighted sound pressure levels when hearing protectors are worn (English PDF)

Foreword

This document complies with the provisions of GB/T 1.1-2020 "Standardization Work Guidelines Part 1: Structure and Drafting Rules of Standardization Documents".

Drafting.

This document is Part 2 of GB/T 7584 "Acoustic Hearing Protectors". GB/T 7584 has the following parts published.

---Part 1: Subjective Methods for Sound Attenuation Measurement;

---Part 2: Effective A-weighted sound pressure level estimation when wearing hearing protection;

---Part 3: Measuring Insertion Loss of Over-Ear Hearing Protectors Using Dedicated Acoustic Testing Equipment

---Part 5: Methods for evaluating noise attenuation by inexperienced subjects wearing the device;

---Part 6: Measurement of sound attenuation in active noise-canceling earmuffs.

This document replaces GB/T 7584.2-1999 "Acoustic Hearing Protectors - Part 2: Effective A-weighted Sound Pressure Level When Wearing Hearing Protectors".

Compared with GB/T 7584.2-1999, the main technical changes in the "Estimation" standard, apart from structural adjustments and editorial modifications, are as follows.

---The definition of "protection rate" has been changed (see 3.1, 1999 edition 3.1);

---The term "assumed protection value" and its definition have been added (see 3.4);

---The term "pink noise" and its definition have been removed (see 3.8 of the 1999 edition);

---The calculation formulas for high, mid, and low frequency sound attenuation have been modified (see 7.2, 7.1 in the 1999 edition);

---The calculation formula for the single-value assessment method has been changed (see 8.2, 8.1 in the 1999 edition).

This document is equivalent to ISO 4869-2:2018 "Acoustic hearing protection - Part 2: Effective A-weighted sound pressure level when wearing hearing protection".

Estimate.

Please note that some content in this document may involve patents. The issuing organization of this document assumes no responsibility for identifying patents.

This document was proposed by the Chinese Academy of Sciences.

This document is under the jurisdiction of the National Acoustics Standardization Technical Committee (SAC/TC17).

Introduction

Hearing protectors are typically used to reduce noise exposure to the ears. Based on their construction, hearing protectors can be classified into earplugs, earmuffs, and helmets, among others.

According to their working method, hearing protectors can be divided into passive noise cancellation (also known as passive noise cancellation) and active noise cancellation (also known as active noise cancellation).

GB/T (Z)7584 "Acoustic Hearing Protectors" aims to specify a standardized method for measuring the sound attenuation of hearing protectors, so as to compare similar conditions in different situations.

The product performance data obtained under the specified conditions are compared. GB/T (Z)7584 is proposed to consist of 6 parts.

---Part 1: Subjective Methods for Measuring Sound Attenuation. The aim is to specify the methods for measuring the sound attenuation of hearing aids at the hearing threshold under laboratory conditions.

The subjective method of reduction.

---Part 2: Effective A-weighted sound pressure level estimation while wearing hearing aids. The aim is to provide several estimation methods based on Part 1.

The sound attenuation test results are used to assess the equivalent exposure sound pressure level experienced when wearing hearing protectors.

---Part 3: Measurement of Insertion Loss of Over-Ear Hearing Protectors Using Dedicated Acoustic Testing Equipment. The purpose is to conduct specialized acoustic testing...

The equipment is standardized so that product performance consistency can be investigated during product type approval testing or certification procedures.

---Part 4: Measurement of the effective sound pressure level of the acoustic restoration earmuffs in relation to sound level. The purpose is to specify the acoustics used in Part 3.

A physical testing method for determining the sound level-dependent sound restoration earmuff attenuation using a testing device or head and torso simulator.

---Part 5: Methods for evaluating noise attenuation through inexperienced participants wearing the device. The aim is to provide an assessment of noise attenuation in occupational environments.

Methods for measuring the sound attenuation performance of a body system (including hearing protectors, subjects, wearers, and instructors).

---Part 6: Measurement of Sound Attenuation in Active Noise-Canceling Hearing Muffs. The aim is to provide information on the active insertion loss of active noise-canceling hearing muffs.

Loss testing methods and total sound attenuation calculation methods.

This document assesses the "effective" sound level when wearing hearing aids, that is, in the absence of the listener, using the center of the head as the measurement point.

The equivalent exposure sound pressure level is obtained by subtracting the hearing protection attenuation value from the A-weighted sound pressure level. Assessing the effective sound level is necessary because it needs to be based on noise exposure...

The exposure limit standard is used to assess the degree of noise hazard. The difference between the effective sound level and the actual sound pressure level in the ear canal lies in the fact that the former is transmitted through the open ear's free field.

The recursive function is converted into a sound field value. The effective sound level is usually 5 dB to 10 dB lower than the sound pressure level in the ear canal, depending on the difference in the incident noise spectrum.

Ideally, the effective A-weighted sound pressure level when wearing hearing protectors is based on the octave band sound attenuation data of the hearing protector (according to...).

The estimation is based on the method specified in ISO 4869-1 (measurement) and the octave band sound pressure level of its noise. However, in many cases, humans...

We may not be able to obtain octave band sound pressure level information for the noise. Therefore, for many practical applications, we can only use simple methods, i.e., only...

This document uses A-weighted and C-weighted sound pressure levels to estimate the effective A-weighted sound pressure level while wearing hearing aids. It addresses the two applications described above.

Furthermore, the regulations specify an octave band calculation method and two optional simplified calculation methods. the high, medium, and low frequency attenuation method (HML method) and the single-value evaluation method (simplified method).

(Referred to as SNR method).

The octave band method requires knowledge of the octave band sound pressure level at the work location and the sound attenuation data of the hearing aid under test. Although this method can be considered...

An "accurate" reference method, however, uses the average sound attenuation and standard deviation of the entire subject group, rather than the sound attenuation of a single subject.

Since the attenuation is based on the data, this method has inherent inaccuracies.

The HML method specifies three sound attenuation values. H (high-frequency attenuation), M (mid-frequency attenuation), and L (low-frequency attenuation). These values are derived from...

The sound pressure level is determined from the octave band sound attenuation data of the hearing aid. These values, along with C-weighted and A-weighted sound pressure levels, are used to calculate the sound pressure level when wearing hearing aids.

Effective A-weighted sound pressure level.

The Sound Noise Ratio (SNR) method specifies a single sound attenuation value, also known as a single-value rating. It is determined from octave band sound attenuation data of the hearing aid.

The effective A-weighted sound pressure level when wearing hearing protection is obtained by subtracting the single-value rating from the C-weighted sound pressure level.

Because the sound attenuation varies greatly among individuals wearing hearing protectors, the accuracy of the three methods mentioned above is essentially equal in most noise conditions.

Even the simplest SNR method can provide a reasonable and accurate effective A-weighted sound pressure level estimate, which helps in the selection and evaluation of hearing protectors.

However, for special cases of extremely high frequency noise or extremely low frequency noise, it is necessary to use the HML method or octave band method.

Appendix A provides an example of calculating the assumed protection value, while Appendices B, C, and D provide examples using the octave band method and the HML method, respectively.

An example of calculating the effective A-weighted sound pressure level when wearing a certain hearing aid using the SNR method.

Different protection rates can be obtained by selecting different parameters during the calculation process. It is important to note that the protection rates of these three methods...

The value is only valid in the following cases.

---The hearing protector was worn correctly and in the same manner as the test subjects during the ISO 4869-1 test;

---Properly maintain your hearing protectors;

---The ear anatomy of the subjects participating in the ISO 4869-1 test is consistent with that of the actual population wearing hearing protection.

Therefore, when using the three methods described in this document, the potential inaccuracies mainly stem from the basic inputs of the ISO 4869-1 test.

Data. If the input data fails to accurately describe the level of protection available to the target population, then no calculation method can provide sufficient data.

The accuracy.

Appendix E describes the uncertainty of the attenuation value and rating.

Note. For comparable hearing protectors, it is meaningless to compare their quality if the effective sound pressure level difference is less than or equal to 3dB.

Acoustic hearing protection, Part 2.

Effective A-weighted sound pressure level estimation when wearing hearing protection

1 Scope

This document describes three methods for estimating the effective A-weighted sound pressure level when wearing hearing aids (octave band method, HML method, and SNR method).

These three methods are applicable to both noise sound pressure level and noise equivalent continuous sound pressure level. The methods specified in this document are mainly applicable to...

Steady-state noise exposure is also applicable to noise containing impulse components. This document may not be suitable for measurements using peak sound pressure levels.

Octave band values, H values, M values, L values, or SNR values are suitable for establishing sound attenuation evaluation standards to facilitate the selection and comparison of hearing aids.

Establish minimum requirements for sound attenuation.

2 Normative references

The contents of the following documents, through normative references within the text, constitute essential provisions of this document. Dated citations are not included.

For references to documents, only the version corresponding to that date applies to this document; for undated references, the latest version (including all amendments) applies.

This document.

GB/T 21230-2014 Acoustics - Determination of Occupational Noise Exposure - Engineering Method (ISO 9612:2009, IDT) ISO 4869-1 Acoustics – Hearing protectors – Part 1: Subjective method for measuring sound attenuation Note. GB/T 7584.1-2026 Acoustic hearing aids - Part 1: Subjective method for measuring sound attenuation (ISO 4869-1:2018, IDT) IEC 61672-1 Electroacoustics - Sound level meters - Part 1: Specification Specifications) Note. GB/T 3785.1-2023 Electroacoustic sound level meters - Part 1: Specifications (IEC 61672-1:2013, IDT)

3 Terms and Definitions

The terms and definitions defined in ISO 4869-1, as well as the following terms and definitions, apply to this document.

The URLs for the terminology databases maintained by ISO and IEC for standardization are as follows.

The percentage of people whose protection is equal to or greater than the design value, indicated by subscripts representing different solution methods.

Examples of these are. APVfx, Hx, Mx, Lx, and SNRx.

Note. The protection rate is usually selected as 84% [equivalent to a constant alpha=1 (see Chapter 5)].

L'p,Ax

The effective value of the A-weighted sound pressure level when wearing hearing aids, given a selected protection rate x and a noisy environment.