Institute of Ergonomics and Hygiene OHTA Learning Portal

Institute of Ergonomics and Hygiene

OHTA503 Course Learning Page

OHTA503: Noise – Measurement and its Effects

Welcome to your IEH course learning page for OHTA503. Use the tabs below to start with the course overview, read the manual, watch video lessons, follow the chapter guide, review the course roadmap, prepare for practical work, discuss case studies and access tools and resources.

Course Overview

This learning page is organised around your study journey. Start with the overview, then use the course manual, video lessons, chapter guide, course roadmap, practical activities, case studies and tools whenever you need to prepare, practise or revise.

Start Here

Course Home

Understand the course outcomes, student manual chapters, assessment expectations and course arrangements.

Study Flow

Learn in Sequence

Move from sound and hearing fundamentals, to measurement and surveys, then to controls, hearing conservation and practical application.

Assessment

Prepare Early

Use the course manual, chapter map, practical guidance, case discussions and revision resources to prepare for the final assessment.

Course Roadmap

You will progress from the basic concepts of sound and hearing, to noise measurement and assessment, then to control and hearing conservation. The course ends with practical application, Q&A, revision and assessment.

Step 1

Understand Sound and Hearing

Build your confidence in frequency, amplitude, wavelength, sound pressure, sound power, decibels, weighting and the ear’s response to sound.

Step 2

Measure and Assess Noise

Learn how survey planning, sound level meters, dosimeters, calibrators, LAeq, exposure normalisation and comparison with criteria are used in occupational noise assessment.

Step 3

Control and Manage Risk

Connect measurement findings to engineering controls, administrative controls, hearing protection, audiometry, reporting and record keeping.

Step 4

Apply, Revise and Prepare

Use instruments and a workplace scenario to produce a measurement plan, field record, exposure interpretation and recommended controls. You will then consolidate your learning through revision and Q&A.

Chapter Guide

Use this chapter guide as a quick reference to what each part of the OHTA503 student manual covers. It is intended to help you understand the purpose of each chapter and decide where to refer when revising specific topics.

Chapter	Title	Chapter Introduction
Chapter 1	Course Overview	Introduces the aim of OHTA503, the expected learning outcomes and the overall scope of the module.
Chapter 2	The Physics of Sound	Explains the basic science behind sound, including propagation, frequency, wavelength, amplitude, sound pressure, sound power, decibels, weighting and human response to sound.
Chapter 3	Risk Assessment and Noise Surveys	Covers occupational noise management, acoustic parameters, exposure assessment, legislation, instrumentation, calibration, dosimetry and the main types of workplace noise surveys.
Chapter 4	Noise Control Engineering	Introduces practical approaches for reducing noise at source, along the transmission path and at the receiver, including engineering and administrative controls.
Chapter 5	Hearing Protector Programme	Describes hearing protection devices, selection methods, attenuation ratings, fitting, fit checking, training, maintenance and programme requirements.
Chapter 6	Education and Training	Explains the role of information, instruction and training in helping workers and competent persons manage occupational noise risks effectively.
Chapter 7	Audiometric Testing	Introduces hearing disorders, noise-induced hearing loss, audiometric programmes, audiograms, test validity and monitoring intervals.
Chapter 8	Reporting and Record Keeping	Outlines the records and documentation needed for noise assessments, hearing protector programmes, audiometric monitoring and ongoing risk management.
Chapter 9	Guidelines for an Effective Hearing Conservation Programme	Brings together exposure assessment, control measures, hearing protection, training, audiometry and programme review into an integrated hearing conservation approach.
Chapter 10	Introduction to Environmental Noise	Provides an overview of environmental noise concepts, community noise response, outdoor sound propagation and environmental noise measurement.
Chapter 11	References	Lists references, standards and further reading that support the technical content of the manual.

Course Manual

Use the embedded OHTA503 student manual as your main course reference. You can read it directly on this page while using the other tabs for lesson planning, chapter guidance, practical preparation and revision support.

Open manual in a new tab Download manual

Study note: If the PDF does not display on your device, use the open or download button above. Some mobile browsers and security settings may block embedded PDF previews.

Video Lessons

Use these video lessons to review the main OHTA503 learning themes before class, during practical preparation or while revising after lessons. Select a lesson from the list to load it into the video player.

Video 1: The Threat of Noise

Introduces noise as a workplace health hazard, its effects on people, and why noise risk needs to be recognised and controlled.

Video note: Select a video lesson from the list to load it into the main video player.

Practical & Revision

This section helps you prepare for the hands-on practical activities and revision. You will apply the occupational hygiene process: plan, measure, interpret, recommend and report. You will also have time to ask questions, revise key topics and prepare for the assessment.

Instrument Station

Sound Level Meter and Calibrator

Identify the microphone, windscreen, weighting and time response settings.
Conduct a pre-measurement field check.
Measure LAeq, Lmax and LCpeak where available.
Conduct a post-measurement field check.

Instrument Station

Noise Dosimeter

Check the dosimeter configuration and exchange rate setting.
Practise correct microphone placement near the hearing zone.
Review start/stop steps, field notes and observation requirements.
Interpret dose or exposure output.

Case Station

Workplace Noise Survey Case

Identify noisy tasks and similar exposure groups.
Select the appropriate survey type and instrument.
Plan measurement locations and durations.
State assumptions and limitations clearly.

Reporting Station

Interpretation and Control Advice

Compare results with relevant exposure criteria.
Recommend engineering and administrative controls.
Advise on hearing protection and audiometry needs.
Prepare a concise verbal report for a workplace scenario.

Revision Block

Q&A and Course Revision

Clarify difficult concepts from Chapters 2 to 10.
Review common calculation and interpretation mistakes.
Revisit instrument settings, field checks and survey strategy.
Summarise key learning points before the assessment.

Exercise Question Bank

Practical and Revision Exercise Window

Use this window to access additional exercise questions, worksheets and revision materials. Open the relevant file during class or use it for self-study after the lesson.

Access note: The exercise folder is embedded below. If the files do not display, open the Google Drive folder in a new tab and check that the folder sharing is set to viewer access for students.

Open exercise folder in Google Drive

Case Studies

Use this section for guided case studies and class discussion. Select a case study below, review the scenario and data, then work through the discussion questions with your group.

Case Study 2

Noise Risk Management at The Artisan Woodshop

Objective: Apply the principles of noise assessment, hierarchy of controls and implementation of a Hearing Conservation Programme in a small-scale industrial setting.

Scenario: The Artisan Woodshop is a custom furniture manufacturing facility. During a preliminary walk-through survey, the supervisor noted that workers often need to raise their voices to be heard at arm’s length. This suggests that workplace noise levels may be above 80 dBA. You have been tasked to perform a detailed assessment for the lead Carpenter.

Artisan Woodshop case study visual showing a woodworking environment with potential noise sources — Case visual A: Review the woodshop environment and identify the likely high-noise tasks and equipment.

Artisan Woodshop case study visual showing woodworking noise exposure and control considerations — Case visual B: Consider how task duration, equipment noise and worker position affect the Carpenter’s daily exposure.

Task-Based Noise Data

An individual noise assessment was conducted by shadowing the Carpenter through a typical 8-hour shift. The following task-based measurements were recorded.

Job Activity	Duration (min)	Measured LAeq,T (dBA)
Router	120	96.0
Jointer	60	93.0
Band Saw	30	95.0
Lathe	90	89.0
Hammering	30	89.0
Planer	60	88.0
Clean-up	30	82.0
Lunch / Breaks	60	65.0

Part A

Exposure Assessment

Calculate the 8-hour normalised daily exposure for the Carpenter.
Compare the calculated exposure with the recommended 8-hour exposure limit of 85 dBA.
Identify which task contributes most to the Carpenter’s total noise dose.
Discuss why task duration and sound level must both be considered.

Discussion hint: The calculated 8-hour normalised exposure is 92 dBA. The Router is the largest contributor and accounts for over 317% of the allowable dose on its own.

Part B

Hierarchy of Controls

Propose at least two engineering control options for the Router or Band Saw.
Explain how source, path and receiver controls could be applied in this woodshop.
Suggest administrative controls that could reduce the Carpenter’s individual exposure.
Discuss whether job rotation alone is an adequate long-term control strategy.

Discussion hint: Possible options include acoustic enclosures, vibration isolation mounts, a Buy Quiet policy, job rotation and designated quiet refuge areas for breaks and paperwork.

Part C

Hearing Protection Devices

Select an appropriate hearing protector class for an LAeq,8h of 92 dBA using the AS/NZ classification approach.
Discuss what should be done if the Carpenter finds foam earplugs uncomfortable.
Explain why removing hearing protection for short periods can significantly reduce effective protection.
Identify what fitting and training points should be reinforced.

Discussion hint: An exposure between 90 and 95 dBA generally requires a Class 2 hearing protector under the AS/NZ classification approach. Training should include correct insertion technique, such as the pinna pull method for foam earplugs.

Part D

Audiometric Monitoring

The Carpenter’s annual audiogram shows a 12 dB shift in the average of 2000, 3000 and 4000 Hz compared with baseline. Discuss whether this is a Standard Threshold Shift.
Identify what actions should be taken after a Standard Threshold Shift is identified.
Explain why refitting, retraining and retesting may be necessary.
Discuss how audiometry findings should trigger review of the overall Hearing Conservation Programme.

Discussion hint: A shift of 10 dB or more at the average of 2000, 3000 and 4000 Hz is treated as a Standard Threshold Shift. Follow-up should include refitting, retraining and retesting within 30 days on rested ears where applicable.

Group output: Prepare a short response covering the calculated exposure, main contributing task, recommended engineering controls, administrative controls, hearing protection approach, audiometric follow-up and key reporting points.

Case Study 1

Risk Assessment and Sampling Strategy at Metro Metal Fabrication

Objective: Apply occupational noise risk assessment principles and design an appropriate sampling strategy for a medium-sized metal fabrication facility with new equipment and changed work schedules.

Scenario: Metro Metal Fabrication recently underwent a major upgrade. A new High-Speed Stamping Press was installed, and the Welding and Grinding department was expanded. The previous noise survey is three years old and does not include the new equipment.

The plant manager has observed that supervisors in the stamping area must raise their voices and stand at arm’s length to be understood. The fabrication team now works 12-hour shifts, four days a week, instead of the previous 8-hour schedule. You are the Occupational Hygienist tasked with conducting a new risk assessment and designing a noise sampling plan.

Metro Metal Fabrication case study visual showing the metal fabrication workplace context — Case visual A: Review the work environment and consider where preliminary observations should be made.

Metro Metal Fabrication case study visual showing noise sampling considerations in the workplace — Case visual B: Consider how worker movement, fixed workstations and noise sources affect the sampling strategy.

Challenge 1

Preliminary Risk Assessment

Does the observation that supervisors must raise their voices at arm’s length justify a detailed noise survey?
Explain why this observation is a useful screening indicator during a walk-through survey.
How does the change to 12-hour shifts affect the risk assessment compared with a standard 8-hour workday?
Discuss why longer shifts may increase concern even when measured sound levels appear similar.

Discussion hint: The need to raise voices at arm’s length suggests that levels may be greater than 80 dBA, which supports conducting a detailed assessment. Longer shifts reduce recovery time for the hearing mechanism, and adjustment may be needed to account for increased exposure duration.

Challenge 2A

Sampling Plan: Stamping Area

Conditions: The stamping press operates in a consistent, cyclical pattern. There are three fixed workstations around the machine.

Propose a suitable sampling plan for the stamping area.
Decide whether an area/equipment survey using a Type 1 or Type 2 sound level meter is appropriate.
Discuss whether predictive modelling based on the stamping cycle duration could be useful.
Explain why an area survey may be sufficient where noise is consistent and workers are at fixed locations.

Discussion hint: An area or equipment survey may be appropriate because the noise pattern is consistent and the workstations are fixed. Measurements should represent the worker positions and the typical operating cycle.

Challenge 2B

Sampling Plan: Fabrication and Grinding Team

Conditions: Fifteen workers move between grinding stations, welding booths and a tool room. Their tasks vary daily based on custom orders.

Propose a suitable sampling plan for workers with variable tasks and movement patterns.
Discuss representative worst-case monitoring by selecting 3-5 of the highest-exposed workers for dosimetry.
Discuss whether statistical monitoring could be used to identify the top 20% of noise-exposed individuals with a 95% confidence level.
Identify the appropriate instrument for this group.

Discussion hint: Personal noise dosimeters should be used and worn for as close to the entire shift as practical. Dosimetry is more suitable where workers move around and tasks vary throughout the day.

Challenge 3

Instrumentation and Quality Control

What field check must be performed with an acoustical calibrator before and after the survey?
What should be done if the post-survey check is outside acceptable limits?
Where should dosimeter microphones be placed on fabrication workers?
What field observations should be recorded during the survey?

Discussion hint: A field check should be performed before and after the survey. If the post-survey check is outside limits, for example +/- 2 dB for Class 2 instrumentation, the data may be invalid and the measurement should be repeated. Dosimeter microphones should be placed near the hearing zone, such as the upper shoulder or shirt collar, and should not be covered by clothing.

Challenge 4

Reporting and Decision Making

After data collection, the LAeq,8h for a Grinder is calculated as 88 dBA.

Compare this result with the commonly recommended 8-hour exposure limit of 85 dBA.
Explain whether further action is required.
Apply the hierarchy of controls and identify what should be considered before relying on PPE.
Identify what should be included in the report to support decision making.

Discussion hint: An LAeq,8h of 88 dBA exceeds the commonly recommended 85 dBA limit. PPE should be treated as the last resort if engineering and administrative controls are not feasible or sufficient.

Group output: Prepare a sampling strategy for the stamping area and the fabrication/grinding team. Include your survey justification, instrument selection, calibration requirements, microphone placement, interpretation of the 88 dBA result, and recommended next steps using the hierarchy of controls.

Case Study 3

Noise Control Decision and Hearing Protection Selection at Precision Packaging

Objective: Apply the hierarchy of controls to select practical noise control measures and choose suitable hearing protection as an interim or supplementary control.

Scenario: Precision Packaging operates a production line with a bottle unscrambler, compressed air cleaning station, conveyor transfer points and an end-of-line case packer. A recent noise survey found that the Packaging Operator has an 8-hour normalised exposure of 91 dBA. Management wants immediate recommendations because the line cannot be stopped for a major redesign this month.

Measured Noise Information

The following information was collected during a detailed survey and observation of the operator’s normal work pattern.

Source / Activity	Measured Level	Observation	Possible Control Direction
Compressed air cleaning	97 dBA	Short but frequent use; open nozzle directed at bottles and machine parts.	Substitution, engineering control, work practice control.
Bottle unscrambler	94 dBA	Continuous mechanical impact and vibration from bottles contacting metal surfaces.	Source control, damping, maintenance, enclosure.
Conveyor transfer points	89 dBA	Intermittent impact noise from containers and product flow.	Low-noise materials, isolation, layout improvement.
Case packer	92 dBA	Repeating mechanical cycle; operator stands nearby for inspection and clearing jams.	Guarding/enclosure, distance, automation, maintenance.
Quiet inspection desk	74 dBA	Operator completes paperwork here for approximately 45 minutes per shift.	Noise refuge and task scheduling.

1/1 Octave Band Noise Data

Use the octave band data below to support discussion on source diagnosis, engineering control selection and hearing protector suitability. Values are 1/1 octave band sound pressure levels in dB re 20 µPa.

Octave Band Centre Frequency	Compressed Air Cleaning Overall LAeq,T: 97 dBA	Bottle Unscrambler Overall LAeq,T: 94 dBA	Case Packer Overall LAeq,T: 92 dBA
63 Hz	68	79	75
125 Hz	74	83	79
250 Hz	80	85	83
500 Hz	86	87	85
1,000 Hz	89	88	87
2,000 Hz	91	89	86
4,000 Hz	92	86	83
8,000 Hz	87	81	78

Interpretation prompt: Compressed air cleaning is strongest in the higher frequency bands, which supports considering low-noise nozzles, air pressure reduction, shielding or substitution. The bottle unscrambler and case packer show broader mid-frequency content, which supports considering damping, isolation, maintenance, acoustic lining, partial enclosure and layout changes.

Part A

Control Decision Using the Hierarchy of Controls

Identify which noise sources should be prioritised for control.
Classify possible controls as elimination, substitution, engineering, administrative or PPE.
Explain why PPE should not be treated as the first or only control.
Separate immediate actions from medium-term engineering actions.

Discussion hint: Compressed air cleaning and the bottle unscrambler are strong priorities because they are high-level and potentially controllable at source. PPE may be needed immediately, but engineering and administrative controls should still be pursued.

Part B

Engineering and Administrative Control Selection

Propose two engineering controls for compressed air cleaning.
Propose two engineering controls for the bottle unscrambler or case packer.
Suggest one administrative control that reduces time spent near the highest noise sources.
State what information you would need before confirming the final control design.

Discussion hint: Possible controls include low-noise compressed air nozzles, reducing air pressure, partial enclosure, acoustic lining, vibration damping, maintenance, isolation pads, relocating inspection tasks, planned quiet periods and use of the quiet inspection desk as a refuge.

Part C

Hearing Protection Device Selection

The operator’s LAeq,8h is 91 dBA. Three hearing protector options are available:

Option 1: Reusable earplug, estimated protection 10 dB.
Option 2: Foam earplug, estimated protection 18 dB.
Option 3: Earmuff, estimated protection 24 dB.

Select a suitable option and explain your reasoning. Consider under-protection, overprotection, comfort, communication, compatibility and correct fitting.

Discussion hint: The best choice is not always the highest attenuation. A suitable HPD should reduce exposure to an acceptable range while still allowing communication and warning signals to be heard. Fit, comfort and consistent use are critical.

Part D

Implementation and Verification

How would you check whether the selected controls are effective?
What training should be provided to the Packaging Operator?
What records should be kept after implementing controls and issuing HPDs?
When should the noise assessment be reviewed?

Discussion hint: Follow-up measurements should be carried out after engineering controls are installed. HPD training should include selection, fitting, limitations, maintenance and the effect of removing protection during exposure. Records should include survey results, control decisions, HPD issue, training and review actions.

Group output: Prepare a control action plan that prioritises noise sources, recommends engineering and administrative controls, selects a suitable HPD, explains why it was selected, and identifies how effectiveness will be verified.

Tools & Resources

Use this section as your OHTA503 resource library. It brings together the course manual, IEH digital tools, official guidance links, key formulas, standards, practical field reminders and glossary terms for occupational noise assessment.

Featured Tools

Occupational Noise Digital Tools

Use these IEH tools as practical companions when thinking through survey planning, measurement records, exposure interpretation, calculation practice, control selection and reporting.

Open assessment toolkit Open OHTA 503 Learning Tool

How to use this tab

Before, During and After Class

Before class: review terminology, formulas and relevant manual chapters.
During class: use the tools, case studies and official links to support discussion.
After class: practise calculations, revisit standards and prepare for assessment.

Manual

Core Study Reference

Use the OHTA503 student manual as the main reference. Revisit Chapters 2 to 5 when practising calculations, exposure assessment, noise control and hearing protector selection.

Calculators

Calculation Practice

Practise decibel addition, logarithmic averaging, LAeq,8h / LEX,8h normalisation, noise dose, task-based exposure and hearing protector protected level estimates.

Open OHTA 503 Learning Tool

Fieldwork

Practical Survey Support

Use this tab to review instrument settings, calibration checks, microphone placement, observation notes, sampling strategy and reporting requirements before practical work.

Official guidance links: These links support your learning and help you connect OHTA503 principles to workplace practice. Requirements differ between jurisdictions, so always check the applicable national law and company requirements before making professional decisions.

Singapore

Singapore WSH and MOM References

International

Occupational Noise Guidance

Key Formulas and Calculation Reminders

Topic	Formula / Reminder	Student Use
Decibel addition	Ltotal = 10 log10(10^(L1/10) + 10^(L2/10) + …)	Use when combining independent noise sources or octave band levels.
Logarithmic average	Lavg = 10 log10[(1/n) × Σ10^(Li/10)]	Use for repeated measurements where a logarithmic average is required.
Task-based LAeq,T	LAeq,T = 10 log10[(1/T) × Σ ti × 10^(Li/10)]	Use when exposure varies across tasks or work areas.
Normalised daily exposure	LEX,8h = LAeq,Te + 10 log10(Te / 8)	Use to normalise exposure to a nominal 8-hour working day.
3 dB exchange rule	Every 3 dB increase represents a doubling of sound energy.	Use this to explain why small dB changes can be occupationally important.
Peak noise	Check LCpeak where impulsive or impact noise may be present.	Use when assessing punch presses, impacts, explosive sounds or sudden high-level events.

Standards and Reference Documents

The standards below are useful references for occupational noise measurement, hearing impairment estimation, instrument specifications, construction noise control and machinery noise emission assessment. Students should understand what each standard is generally used for, even if the full standard is not provided as course material.

ISO

Measurement and Assessment Methodology

ISO 9612: Determination of occupational noise exposure using the engineering method.

ISO 1999: Estimation of noise-induced hearing impairment.

SS 602: Singapore Code of practice for noise control on construction and demolition sites.

IEC

Equipment Specifications

IEC 61672-1: Specifications for sound level meters, including Class 1 and Class 2 instruments.

IEC 61252: Specifications for personal sound exposure meters, commonly used as noise dosimeters.

IEC 60942: Specifications for sound calibrators.

M/E

Machinery and Equipment Standards

ISO 4871: Declaration and verification of noise emission values.

ISO 3744: Determination of sound power levels using sound pressure.

ISO 11201: Measurement of emission sound pressure levels at work stations.

Practical Fieldwork Checklist

Before Survey

Plan and Prepare

Confirm purpose of survey and exposure criteria.
Review processes, tasks, work schedules and worker groups.
Select area survey, task-based assessment or personal dosimetry.
Check instrument class, battery, calibration status and settings.

During Survey

Measure and Observe

Conduct pre-use field check with the acoustical calibrator.
Record LAeq,T, LCpeak where applicable, duration and task details.
Place dosimeter microphones near the hearing zone and avoid clothing contact.
Document abnormal conditions, production rate and worker movement.

After Survey

Interpret and Report

Conduct post-use field check and review any drift.
Normalise exposure to LAeq,8h / LEX,8h where required.
Compare results with applicable criteria and action levels.
Recommend controls using the hierarchy of controls.

Glossary of Key Terms

LAeq,T

A-weighted equivalent continuous sound level over a specified measurement period.

LEX,8h / LAeq,8h

Noise exposure normalised to a nominal 8-hour working day.

LCpeak

C-weighted peak sound pressure level used when assessing peak or impulsive noise.

SLM

Sound level meter used to measure sound pressure levels in workplace or environmental settings.

Dosimeter

Personal sound exposure meter worn by a worker to measure exposure over time.

HPD

Hearing protection device, such as earplugs, earmuffs or combined protection.

NRR / SNR / HML

Common hearing protector rating approaches used to estimate protected exposure.

HCP

Hearing Conservation Programme covering assessment, controls, HPD, training, audiometry and review.

STS

Standard Threshold Shift, used in audiometric monitoring to identify significant hearing threshold changes.

Resource note: The resources in this tab are provided to support learning and practical application. The OHTA503 student manual remains your primary course reference. Always refer to applicable legal requirements, relevant standards and professional judgement when applying these resources in workplace practice.

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