Hearing

AMA5 Chapter 11 (p 245) applies to the assessment of permanent impairment of hearing, subject to the modifications set out below. Before undertaking an impairment assessment, users of the Guidelines must be familiar with:

• the Introduction in the Guidelines
• the appropriate chapter(s) of the Guidelines for the body system they are assessing.
• the National Acoustic Laboratories Report No. 118 January 1988 ‘Improved procedure for determining percentage loss of hearing’.

The Guidelines take precedence over AMA5.

Assessment of hearing impairment (hearing loss)

9.1 A worker may present for assessment of hearing loss for compensation purposes before having undergone all or any of the health investigations that generally occur before assessment of permanent impairment. For this reason, and to ensure that conditions other than ‘occupational hearing impairment’ are precluded, the medical assessment should be undertaken by an ear, nose and throat specialist or other appropriately qualified medical specialist. The medical assessment needs to be undertaken in accordance with the hearing impairment section of AMA5 Table 11-10 (pp 272–275). The medical specialist performing the assessment must examine the worker. The medical specialist’s assessment must be based on medical history and ear, nose and throat examination, evaluation of relevant audiological tests, and evaluation of other relevant investigations available to the medical assessor. Only medical specialists can sign medical reports.

9.2 Disregard AMA5 sections 11.1b and 11.2 (pp 246–55), but retain Section 11.1a, ‘Interpretation of symptoms and signs’ (p 246).

9.3 Some of the relevant tests are discussed in the AMA5 hearing impairment evaluation summary in AMA5 Table 11-10 (pp 272–75). The relevant row for the Guidelines is the one headed ‘hearing impairment’, with the exception of the last column, headed ‘degree of impairment’. The degree of impairment is determined according to the Guidelines.

9.4 The level of hearing impairment caused by non-work-related conditions is assessed by the medical specialist and considered when determining the level of work-related hearing impairment. While this requires medical judgement on the part of the examining medical specialist, any non-work-related deductions should be recorded in the report.

9.5 Disregard AMA5 tables 11-1, 11-2 and 11-3 (pp 247–50). For the purposes of the Guidelines, National Acoustic Laboratory (NAL) tables from the NAL Report No. 118, ‘Improved procedure for determining percentage loss of hearing’ (January 1988) are adopted as follows:

• Tables RB 500-4000 (pp 11–16)
• Tables RM 500-4000 (pp 18–23)
• Appendices 1 and 2 (pp 8–9)
• Appendices 5 and 6 (pp 24–26)
• Tables EB 4000–8000 (pp 28–30) (The extension tables)
• Table EM 4000–8000 (pp 32–34) (The extension tables)

Where an assessor uses the extension tables, they must provide an explanation of the worker’s ‘special requirement to be able to hear at frequencies above 4000 Hz’ (NAL Report No.118, p 6).

In the presence of significant conduction hearing loss, the extension tables do not apply.

AMA5 Table 11-3 is to be replaced by Table 9.1 at the end of this chapter.

Hearing impairment

9.6 Impairment of a worker’s hearing is determined according to evaluation of the individual’s binaural hearing impairment (BHI).

9.7 Permanent hearing impairment should be evaluated when the condition is stable. Prosthetic devices (that is, hearing aids) must not be worn during the evaluation of hearing sensitivity.

9.8 Hearing threshold level for pure tones is defined as the number of decibels above standard audiometric zero for a given frequency at which the listener’s threshold of hearing lies when tested in a suitable sound attenuated environment. It is the reading on the hearing level dial of an audiometer that is calibrated according to Australian Standard AS 2586 1983.

9.9 Evaluation of binaural hearing impairment is determined by using the tables in the 1988 NAL publication with allowance for presbyacusis according to the presbyacusis correction table, if applicable, in the same publication.

The binaural tables RB 500-4000 (NAL publication, pp 11–16) are to be used. The extension tables EB 4000- 8000 (NAL publication, pp 28–30) may be used when the worker has a ‘special requirement to be able to hear at frequencies above 4000 Hz’ (NAL publication, p 6). Where an assessor uses the extension tables, they must provide an explanation of the worker’s special requirement to be able to hear at frequencies above 4000 Hz. For the purposes of calculating binaural hearing impairment, the better and worse ear may vary as between frequencies.

Where it is necessary to use the monaural tables, the binaural hearing impairment (BHI) is determined by the
formula:

BHI = [4 x (better ear hearing loss)] + worse ear hearing loss ÷ 5

9.10 Presbyacusis correction (NAL publication, p 24) only applies to occupational hearing loss contracted by a gradual process (eg occupational noise-induced hearing loss and/or occupational solvent-induced hearing loss). Please note that when calculating by formula for presbyacusis correction (eg when the worker is older than 81), use the formula shown in Appendix 6, line 160 of the NAL publication (p 26), which uses the correct number of 1.79059. Note: there is a typographical error in Table P on p 25 of the NAL publication, where the number 1.79509 is incorrectly used.

9.11 Binaural hearing impairment and severe tinnitus: Up to 5 per cent may be added to the work-related binaural hearing impairment for severe tinnitus caused by a work-related injury:

• after presbyacusis correction, if applicable
• before determining whole person impairment (WPI).

Assessment of severe tinnitus is based on a medical specialist’s assessment.

9.12 Only hearing ear: A worker has an ‘only hearing ear’ if he or she has suffered a non-work related severe or profound sensorineural hearing loss in the other ear. If a worker suffers a work-related injury causing a hearing loss in the only hearing ear of x dB HL at a relevant frequency, the worker’s work-related binaural hearing impairment at that frequency is calculated from the binaural tables using x dB as the hearing threshold level in both ears. Deduction for presbyacusis, if applicable, and addition for severe tinnitus, is undertaken according to the Guidelines.

9.13 When necessary, binaural hearing impairment figures should be rounded to the nearest 0.1%. Rounding up should occur if equal to or greater than 0.05%, and rounding down should occur if equal to or less than 0.04%.

9.14 Table 9.1 in the Guidelines (below) is used to convert binaural hearing impairment, after deduction for presbyacusis if applicable and after addition for severe tinnitus, to WPI.

• The current level of binaural hearing impairment is established by the relevant specialist.
• Convert this to WPI using Table 9.1 in the Guidelines.
• Calculate the proportion of the current binaural hearing impairment that was accounted for by the earlier assessment and express it as a percentage of the current hearing impairment.
• The percentage of current hearing impairment that remains is the amount to be compensated.
• This needs to be expressed in terms of WPI for calculation of compensation entitlement.

Example:

• The current binaural hearing impairment is 8%.
• The WPI is 4%.
• The binaural hearing impairment for which compensation was paid previously is 6%, which is 75% of the current binaural hearing impairment of 8%.
• The remaining percentage, 25% is the percentage of WPI to be compensated.
• Twenty-five per cent of the WPI of 4% is 1% WPI.

9.16 AMA5 examples 11.1, 11.2 and 11.3 (pp 250–51) are replaced by examples 9.1–9.7, below, which were developed by the working party.