Introduction: Two Different Tests, Two Different Purposes

Regulation 58 requires audiometric testing. But what exactly is being tested? The answer is: it depends. There are two distinct types of audiometric tests—baseline and monitoring—each serving a different purpose in a comprehensive hearing protection program.

Understanding the difference is critical. Employers who confuse these two tests, or who use monitoring tests as baselines, undermine the entire purpose of the audiometric testing requirement. This guide explains what each test is, when it is conducted, what it measures, and how they relate to each other in building a defensible audiometric testing program.

Baseline Audiometric Testing: Establishing the Reference

What Is a Baseline Test?

A baseline audiometric test is a hearing test conducted at the beginning of a worker’s employment (or at the beginning of noise-exposed work if the worker was already employed in a non-noise-exposed role). The baseline establishes a reference measurement of the worker’s hearing threshold at a specific point in time—typically before the worker has been significantly exposed to occupational noise.

The baseline is like a starting point. It answers the question: “What was this worker’s hearing like when they began this job?” All future monitoring tests are compared against this baseline to determine whether hearing loss has occurred.

When Must a Baseline Be Conducted?

For a new worker entering a noise-exposed role, the baseline must be completed within three months of commencing employment. This is consistent across all Australian jurisdictions that have adopted Regulation 58 or equivalent:

• NSW: Three months from 1 January 2024 (for existing workers at commencement); three months from hire date (for new workers)
• Queensland: Three months from 29 July 2025 (for existing workers); three months from hire date (for new workers)
• Victoria: Three months from employment commencement (for both new and existing workers)
• Other states: Generally three months from employment commencement or regulation commencement

The three-month window is not arbitrary. It reflects practical experience: a baseline conducted too long after employment commences may already incorporate some occupational noise exposure, compromising its validity as a true baseline.

The Ideal Timing: Pre-Employment vs Early Employment

Ideally, a baseline should be conducted before the worker is exposed to occupational noise. For some roles, this may be possible—the baseline could be conducted as part of a pre-employment medical or during the first week of employment in a quiet period. This creates the most accurate baseline because it represents the worker’s hearing before any occupational exposure.

In many cases, however, the baseline is conducted within the first three months of employment, after some occupational exposure has already occurred. This is acceptable under the regulation, but less ideal.

The 14-Hour Quiet Period Before Baseline Testing

A critical requirement: the worker must have been in a quiet environment (below approximately 70 dB(A)) for at least 14 hours before the baseline test is conducted. This allows temporary threshold shift (TTS) from recent noise exposure to resolve.

If a baseline is conducted while the worker has TTS, the baseline will be artificially lower (worse) than the worker’s true threshold. This creates problems downstream—future monitoring tests may look like they show improvement (the hearing appears to recover) when, in fact, they are simply returning to the worker’s true baseline.

In practice, this means baseline testing should be scheduled after a rest day or early in a work week when the worker has not been in a noisy work environment for at least 14 hours.

What the Baseline Measures

The baseline measures hearing sensitivity (thresholds) at specific frequencies: typically 500, 1000, 2000, 3000, 4000, 6000, and 8000 Hz. The measurement is expressed in decibels of hearing loss (dB HL), with 0 dB HL representing normal hearing.

The baseline audiogram (the graphical representation of these thresholds) becomes the permanent reference point for the worker. Every subsequent monitoring test is compared against this baseline to assess whether hearing loss has occurred.

Monitoring Audiometric Testing: Detecting Change Over Time

What Is a Monitoring Test?

A monitoring (or serial) audiometric test is a hearing test conducted periodically after the baseline has been established. Monitoring tests are conducted at regular intervals to detect whether hearing loss has occurred since the baseline or since the previous monitoring test.

The monitoring test answers the question: “Has this worker’s hearing changed since their baseline (or last monitoring test)?” By comparing hearing thresholds measured at each monitoring test to the baseline, changes become apparent.

Monitoring Frequency: At Least Every 2 Years

Regulation 58 and equivalent state regulations require monitoring audiometric testing at least every 24 months (two years). This is a minimum standard. Depending on the nature and intensity of noise exposure, more frequent monitoring may be appropriate.

When Might More Frequent Monitoring Be Necessary?

• If significant threshold shift (STS) is detected: If a monitoring test reveals hearing loss of 15 dB or more at multiple frequencies compared to the baseline, annual or even 6-monthly monitoring may be appropriate to track the rate of loss.
• If noise exposure is very high: In extremely noisy environments (e.g., 95+ dB(A)), more frequent monitoring (annual) helps detect early warning signs of accelerating loss.
• If multiple workers in a similar role show STS: Cluster detection of STS suggests the noise control program may be inadequate; more frequent monitoring may help identify workers at risk earlier.

What Monitoring Tests Measure

Monitoring tests measure hearing thresholds at the same frequencies as the baseline. The critical element of a monitoring test is the comparison to the baseline. A monitoring test result isolated from a baseline is of limited value; the power of monitoring testing lies in trend detection.

Significant Threshold Shift (STS): What It Is and What to Do

The primary purpose of monitoring audiometric testing is to detect significant threshold shift (STS)—the development of hearing loss that indicates occupational noise exposure is causing permanent damage.

Defining STS

STS is typically defined as a change in hearing thresholds of 15 dB or more at multiple frequencies when comparing a monitoring test to the baseline. This threshold of 15 dB is used in multiple standards and regulatory contexts:

• AS/NZS 1269.4:2014: Uses 15 dB shift at multiple frequencies as one marker for STS
• OSHA (US standard): Defines STS as 10 dB shift at 2000, 3000, 4000, or 6000 Hz, or 15 dB shift at any single frequency
• Safe Work Australia guidance: Aligns with AS/NZS standards, typically 15 dB at multiple frequencies

Different standards use slightly different criteria. The Australian approach (15 dB at multiple frequencies) is somewhat more conservative than the OSHA approach (10 dB at specific frequencies), meaning it is less likely to flag minor variations as “significant.”

Why 15 dB? Accounting for Test Variability

Audiometric testing has inherent test-retest variability. Even if a worker’s true hearing threshold has not changed, repeated tests may show variations of ±5–10 dB due to test conditions, operator variability, or normal fluctuations in the worker’s attention or response. The 15 dB threshold is chosen to exceed this normal variability and flag true biological change in hearing.

When STS Is Detected: Required Actions

Regulation 58 requires that when significant threshold shift is detected, the PCBU must:

1. Notify the worker: Inform the worker of the STS result and what it means for their hearing health.
2. Arrange further assessment: Refer the worker for further audiological assessment or medical advice. This might include assessment by an occupational audiologist or occupational physician to determine the extent of loss and implications.
3. Review noise controls: Assess whether existing engineering and administrative controls are adequate. If multiple workers show STS, this is a red flag that controls may be inadequate.
4. Plan follow-up monitoring: Establish a more intensive monitoring schedule (e.g., annual or semi-annual) to track the rate of loss.
5. Document the response: Record the notification, referral, control review, and follow-up plan in the worker’s audiometric file.

STS does not mean the worker must be dismissed or removed from the role. It means the employer must intensify efforts to protect the worker’s remaining hearing. It is an indicator that current measures are not fully effective.

Privacy and Workplace Implications

When STS is detected, confidentiality is important. Other workers should not be informed of a specific worker’s hearing loss. However, if STS is detected in multiple workers in a particular role or area, this may trigger a broader review of noise controls in that area, potentially visible to other workers.

Some workers worry that disclosing hearing loss will affect their job security or career. Employers should be clear that STS does not automatically mean the worker will be removed from their role. Instead, it triggers a review of controls and support to protect remaining hearing.

Linking Baseline and Monitoring Tests: Record Integrity

For audiometric testing programs to be effective, baseline and monitoring tests must be properly linked and tracked. This requires careful record-keeping and system design.

The Record Linkage Challenge

Imagine a worker changes names (due to marriage), moves between workplaces (but remains employed by the same company), or has inconsistencies in how their name or identification is recorded. Without careful linkage, their baseline and monitoring tests might be treated as belonging to different people, and the entire benefit of monitoring—detecting hearing loss over time—is lost.

Best Practices for Record Linkage

• Unique identifier: Assign each worker a unique identifier (employee ID) that travels with them through different roles or locations within the company. Use this ID as the primary key for linking baseline and all subsequent monitoring tests.
• Standardized naming: Use a standard format for recording worker names (e.g., last name, first name, middle initials) and maintain consistency across all testing events.
• Master file maintenance: Maintain a master file linking employee ID, name, role, noise exposure status, baseline date, and scheduled monitoring dates.
• Testing provider communication: Clearly communicate the unique identifier and worker details to the testing provider. Request that reports reference the identifier prominently.
• Periodic audits: Periodically audit your record system to ensure all baseline-monitoring test linkages are correct and no records are orphaned or lost.

Baseline vs Pre-Employment Testing: What’s the Difference?

Confusion often arises between baseline audiometric testing (required by Regulation 58) and pre-employment audiometric testing (sometimes conducted as part of pre-employment medical assessments). These are related but distinct concepts.

Pre-Employment Testing

A pre-employment audiometric test is conducted before employment commences, often as part of a pre-employment medical assessment. It serves to:

• Establish the worker’s baseline hearing before employment in that role
• Identify any pre-existing hearing loss so it is not attributed to occupational exposure
• Assess whether the applicant is medically fit for the role
• Create a baseline for comparison in the event of future hearing loss claims

Pre-employment testing is often conducted by occupational health services or third-party medical providers and may not always comply with AS/NZS 1269.4:2014 occupational audiometry standards.

Regulation 58 Baseline Testing

The baseline test required by Regulation 58 must be conducted within three months of commencing employment in a noise-exposed role. It must comply with AS/NZS 1269.4:2014. The 14-hour quiet period requirement applies. The baseline serves as the permanent reference for occupational hearing loss monitoring.

How They Relate

In a well-designed program, the pre-employment test and the Regulation 58 baseline are often the same test—conducted at or near employment commencement, complying with AS/NZS 1269.4:2014, in a certified sound booth by a qualified audiometrist. This single test serves both purposes.

However, if a pre-employment test has already been conducted before employment, a separate Regulation 58 baseline test is still required (though it may be conducted within a few weeks of hire, after any acute pre-employment medical is complete).

Managing Long-Tenure Workers Without Prior Baseline

Many employers implementing Regulation 58 for the first time face a challenge: they have workers with 5, 10, 20 years or more in noise-exposed roles, but no baseline audiometric test on file.

The Regulatory Requirement

Regulation 58 requires all noise-exposed workers to have a baseline test. For existing workers, this baseline was to be completed within three months of the regulation’s commencement in the state (e.g., by 31 March 2024 in NSW, or 28 October 2025 in Queensland).

If that deadline has passed and your organization did not conduct baselines for existing workers, you are currently in non-compliance. The remedy is to conduct baseline tests immediately for all affected workers, even if they have been in the role for years.

The Challenge: A “Baseline” After Years of Exposure

When a baseline is conducted for a worker with 10 years in a noise-exposed role, that baseline reflects the worker’s current hearing—which may already include significant hearing loss from occupational exposure. Is this a true “baseline” for occupational hearing loss purposes? Not really, but it is the best baseline available under the circumstances.

Best Practices for Long-Tenure Workers

• Conduct the baseline anyway: Even if the worker has been exposed for years, establish a baseline now. This allows monitoring of future deterioration.
• Note the timing in records: Clearly document that the baseline was conducted years after employment commenced, and note the worker’s tenure in the role. This provides context if hearing loss claims arise later.
• Consider a pre-baseline assessment: If the worker has any pre-existing testing (from pre-employment medical exams, insurance medical, or other sources), obtain and review those records. They may provide additional context about the worker’s hearing status.
• Communicate with the worker: Explain that the baseline is being established now as part of the regulatory program, even though they have been in the role for years. Clarify that this is a normal part of implementing the requirement, not because they are suspected of having hearing loss.
• Intensify monitoring for high-risk workers: If a long-tenure worker’s baseline shows significant hearing loss already, consider annual or semi-annual monitoring rather than the minimum 2-year frequency. This helps document the stability or progression of loss going forward.

Practical Timeline Example: A Complete Cycle

Here is a realistic example of a baseline and monitoring cycle:

• January 2024: Worker commences employment in a noise-exposed role.
• February 2024: Baseline audiometric test is conducted (within the required 3-month window, after the 14-hour quiet period is observed). Result: normal hearing thresholds.
• February 2026: First monitoring test is conducted (2 years after baseline). Result: hearing thresholds are stable; no STS.
• February 2028: Second monitoring test is conducted (4 years from baseline, 2 years from first monitoring). Result: hearing thresholds show 18 dB shift at 3 and 4 kHz. STS is detected.
• February 2028 (action plan): Worker is notified of STS. Referral is arranged to occupational audiologist. Noise controls are reviewed in the worker’s area. Annual monitoring is scheduled going forward (instead of 2-year cycle).
• February 2029: Follow-up monitoring test. Result: no additional deterioration; hearing thresholds are stable.

This example illustrates how baseline and monitoring tests work together to detect and respond to hearing loss over time.

Internal Links: Deepen Your Understanding

• WHS audiometric testing requirements across Australia
• Full explanation of Regulation 58
• How audiometric testing procedures work step-by-step
• Detecting and responding to significant threshold shift

Conclusion

Baseline and monitoring audiometric tests serve distinct but complementary purposes. The baseline establishes a reference measurement of a worker’s hearing at or near employment commencement. Monitoring tests conducted periodically (at least every 2 years) detect changes in hearing over time, allowing early identification of occupational hearing loss.

Proper linkage of baseline and monitoring records is essential. Detection of significant threshold shift requires specific follow-up actions: notification, referral, control review, and intensified monitoring.

For organizations implementing Regulation 58 for the first time, establishing baseline tests for all noise-exposed workers—including long-tenure workers—is the critical first step. From there, a systematic monitoring program can be built to protect workers’ remaining hearing and demonstrate compliance with the regulation.