OSHA vs. MSHA STS Flagging

What Is Flagged, What Is Recordable, and How Soundtrace Handles Both

Hearing conservation programs often operate under both OSHA and MSHA requirements. While the two agencies use similar audiometric data and terminology, they differ in how Standard Threshold Shifts (STS) are recorded, reported, and acted upon.

Understanding these differences is critical for building a compliant and defensible hearing conservation program.

STS Identification Is the Same Under OSHA and MSHA

From a system standpoint, STS identification is consistent across all employees, regardless of regulatory coverage.

In all cases:

• The same baseline audiogram is used.
• The same frequency analysis is applied.
• Hearing thresholds at 2000, 3000, and 4000 Hz are compared to baseline.

A 10 dB average change across these frequencies is flagged as a meaningful shift in hearing sensitivity. This early flag allows employers to identify potential risk and begin review immediately.

At this stage, the shift is identified, but not yet evaluated for recordability or regulatory reporting.

How OSHA Applies STS and Recordability

Under OSHA, an STS is defined as an average 10 dB change at 2000, 3000, and 4000 Hz in either ear, compared to baseline.

However, OSHA separates STS identification from recordability.

A hearing loss is recordable on the OSHA 300 Log only if:

• An STS has occurred, and
• The average hearing level at 2000, 3000, and 4000 Hz is 25 dB HL or greater in the affected ear.

When an OSHA STS occurs, employers must notify the employee within 21 days and implement follow-up actions such as retraining and hearing protection evaluation.

References:
29 CFR 1910.95
29 CFR 1904.10

How MSHA Applies STS and Reporting

MSHA hearing conservation requirements are governed by 30 CFR Part 62.

MSHA uses the same 10 dB average change at 2000, 3000, and 4000 Hz to flag a shift in hearing sensitivity. This functions as an early identification threshold.

However, MSHA distinguishes between:

• A flagged shift, and
• A reportable hearing loss

Under MSHA, a reportable hearing loss occurs when there is an average 25 dB change at 2000, 3000, and 4000 Hz in either ear, relative to baseline or revised baseline.

MSHA is more prescriptive about follow-up actions once a shift is identified, including:

• Retraining
• Hearing protection fit and effectiveness review
• Evaluation of applicable engineering and administrative controls

Employee notification under MSHA must occur within 10 days.

References:
30 CFR Part 62
30 CFR 62.170(c)(2)
https://www.ecfr.gov/current/title-30/chapter-I/subchapter-M/part-62

Illustrative Example: Drilling and Extractive Operations

Consider a company operating drilling rigs and high-noise extraction equipment.

An equipment operator completes annual audiometric testing:

• The results show a 10 dB average change at 2000, 3000, and 4000 Hz.
• The change is flagged immediately by the system.

Under OSHA:

• The shift qualifies as an STS.
• The employee is notified within 21 days.
• The result is not recordable unless the average hearing level also meets the OSHA recordability threshold.

Under MSHA:

• The shift is flagged as an early indicator.
• Follow-up actions are required.
• The result is not reportable unless the average change reaches 25 dB.

In both cases, early identification allows intervention before permanent impairment occurs.

How Soundtrace Handles OSHA and MSHA STS Logic

Soundtrace uses a single, unified STS detection process for all employees.

The only distinction required is whether the employee is covered under OSHA or MSHA, which determines:

• The applicable recordability or reporting threshold
• Notification timing
• Required follow-up actions

Soundtrace:

• Flags STS immediately upon test completion
• Applies the correct OSHA or MSHA logic automatically
• Alerts the audiology team and employer in real time
• Supports timely employee notification
• Documents follow-up actions for compliance and audit readiness

This approach allows employers to operate one hearing conservation program while remaining compliant across regulatory frameworks.

Summary

OSHA and MSHA use the same audiometric data to identify changes in hearing, but they apply different thresholds for recordability, reporting, and follow-up.

Soundtrace bridges that gap by separating identification, regulatory interpretation, and action, helping employers protect workers while simplifying compliance.

Frequently Asked Questions About OSHA and MSHA STS

What is a Standard Threshold Shift (STS)?

A Standard Threshold Shift is identified when there is an average 10 dB change in hearing thresholds at 2000, 3000, and 4000 Hz in either ear compared to a baseline audiogram. This same calculation is used for both OSHA- and MSHA-covered employees.

Is STS identification different under OSHA and MSHA?

No. From a system and audiometric standpoint, STS identification is the same under both OSHA and MSHA. The same baseline comparison and frequency analysis are used. Differences occur only in how the shift is recorded, reported, and acted upon.

What is the difference between STS and recordable hearing loss under OSHA?

Under OSHA, an STS is a 10 dB average change at 2000, 3000, and 4000 Hz. A hearing loss becomes recordable on the OSHA 300 Log only if the STS occurs and the average hearing level at those frequencies is 25 dB HL or greater in the affected ear.

How does MSHA treat STS differently than OSHA?

MSHA uses the same 10 dB average change to flag a shift in hearing sensitivity, but distinguishes between a flagged shift and a reportable hearing loss. Under MSHA, a reportable hearing loss occurs when there is an average 25 dB change at 2000, 3000, and 4000 Hz compared to baseline.

Is an STS always recordable?

No. Under OSHA, an STS is only recordable if it also meets the hearing level threshold for recordability. Under MSHA, a flagged shift does not become reportable unless it meets the MSHA reporting threshold.

How quickly must employees be notified of an STS?

OSHA requires employee notification within 21 days of identifying an STS. MSHA requires employee notification within 10 days. Soundtrace flags STS results immediately upon test completion to support timely review and notification.

Does MSHA require annual audiograms?

Yes. Under 30 CFR 62.170(c)(2), miners enrolled in a hearing conservation program must be offered audiometric testing at intervals not exceeding 12 months.

How does Soundtrace handle OSHA and MSHA STS requirements?

Soundtrace uses a single STS detection process for all employees. The system applies the correct OSHA or MSHA logic automatically based on employee coverage, including recordability thresholds, notification timing, and required follow-up actions.

Why does early STS flagging matter?

Early identification of hearing threshold changes allows employers to intervene before permanent hearing loss occurs. This includes retraining, hearing protection review, and evaluation of noise controls, which aligns with both OSHA and MSHA expectations.