Noise Law and Standards

1. International guidance and frameworks (WHO, ISO, EU/IEC)

These international guidelines and standards are not law in themselves. They are the technical basis that many countries draw on when writing their own law, standards and impact-assessment methods, adapted to national context.

WHO Environmental Noise Guidelines

The WHO Environmental Noise Guidelines were produced by the World Health Organization to assess the effect of noise on public health. They are not simply about whether noise exceeds a legal figure; they focus on the long-term consequences of continuous exposure — sleep disturbance, stress, effects on children's learning, and increased cardiovascular risk.

Assessment therefore uses indicators that reflect long-term exposure, such as Lden (Day-Evening-Night Level) or Ldn (Day-Night Level). Both are 24-hour average levels with a penalty added to evening and night-time noise, reflecting the fact that people are more sensitive to noise at those times than during the day.

In Thailand, environmental noise assessment in some cases uses Ldn (Day-Night Level) as the reference index. It follows the same principle as Lden but divides the periods and applies the weighting according to the applicable requirements. Which indicator applies depends on the law, the standard, or the purpose of the assessment in each project.

The ISO standards

Each standard is written for a specific job. No single one covers every case:

The EU and IEC frameworks set out measurement and reporting methods for environmental work, and the standards for the measuring instruments themselves — for example the accuracy class of a sound level meter.

2. Workplaces and occupational health

In occupational health the important question is not simply “where is it loudest”, but how much noise an employee accumulates across the whole working period. The risk of hearing loss comes from cumulative noise exposure rather than from the level at any single moment.

Dose and TWA (Time-Weighted Average)

Exposure assessment calculates the average level an employee receives across the shift, together with the noise dose and the TWA, using an exchange rate — the rule stating how many decibels of increase counts as a doubling of accumulated exposure. The exchange rate differs between countries' laws and standards, so the instrument must be configured to match the requirement that actually applies, not left on the meter's factory default.

Hearing Conservation Programme

Where the assessment shows employees are exposed above the limit, the employer should put systematic controls in place: periodic audiometric testing, training so that employees understand the risk, and appropriate hearing protection devices selected on their attenuation rating — NRR or SNR — against the actual exposure level.

Documents and records to keep

Managing noise risk requires a complete document trail: measurement results, the engineering control plan (for example insulation or machine enclosures), instrument calibration records, audiometric testing records, and evidence of training and of hearing-protection issue. These are the documents that labour and safety regulators typically ask for during an inspection.

3. Community, environment and urban planning

Environmental and community noise assessment has a different purpose from occupational work. It concerns quality of life and public annoyance, rather than the cumulative dose an individual receives over a working day.

Day/night assessment

Community noise criteria usually set separate limits for day and night, because tolerance for noise changes with the time of day — particularly at night, when noise affects rest and sleep far more.

Average levels and noise events

Beyond the average level (Leq), assessment must also consider the maximum level (Lmax) or specific noise events. A brief loud event — an impact from construction work, a door slamming, a passing truck — can cause more annoyance and more disturbance to residents than continuous noise with the same average.

Planning and managing with noise maps

At city scale or on large projects, a noise map is an essential tool for analysing and predicting how noise spreads, supporting urban planning and control measures: buffer zones between factories and housing, barrier design, building placement, and restricting the hours in which noisy activity is permitted, so that the impact on surrounding communities is reduced.

4. Buildings and architecture (building acoustics)

Building acoustics differs from environmental and occupational assessment. It does not measure the impact of an external source; it assesses how well a building controls sound and creates an acoustic environment suited to its use. It covers three main areas.

1. Sound insulation between spaces

This assesses how well walls, floors, doors and other building elements block sound between rooms or between buildings. Field testing references ISO 16283, and results are converted into ratings under ISO 717 — R′w, DnT,w or L′nT,w — so they can be compared against the project specification and answer the question “how much noise from next door will actually get through?”

2. Room acoustics

Interior acoustic design aims to give a space acoustic conditions suited to its use, above all by controlling reverberation time (RT) under ISO 3382. Different room types need different RT values — a classroom, a meeting room, a theatre and a concert hall are not the same. Speech Transmission Index (STI) is also assessed, measuring speech intelligibility, which matters for classrooms, meeting rooms, video-conference rooms and public address systems.

3. Background noise from building services

Noise from air conditioning, ventilation, lifts, machinery and electrical equipment inside a building may not be loud, but if it is not properly controlled it undermines comfort. Assessment normally uses NC (Noise Criteria) or NR (Noise Rating) to set an acceptable background level for each type of space — offices, classrooms, hotels, hospitals, recording studios. In general, the lower the NC/NR value, the quieter the environment, and the better suited it is to activities needing concentration or clear communication.

5. The Thai law and requirements that apply

International standards are the important technical reference, but a project in Thailand must comply with the law and requirements actually in force. These are structured as a hierarchy, and each level plays a different role.

Acts (พระราชบัญญัติ)

The primary legislation, which sets the principles and gives state agencies the authority to issue subordinate law or specific requirements.

Ministerial Regulations (กฎกระทรวง)

These set out the criteria, procedures and technical requirements enforced under each Act.

Notifications, regulations and agency requirements

These carry the most detail, and usually specify the actual limit values, the measurement method, the assessment method and the practice rules — for example National Environment Board notifications, Department of Health notifications, or Ministry of Industry notifications.

Local ordinances

Local administrative bodies — the Bangkok Metropolitan Administration, municipalities, or sub-district administrations — may issue additional ordinances to control noise appropriately for their area, and in some cases these are stricter than central law.

Deciding which requirements a project must meet therefore cannot rest on a single piece of legislation. All the relevant Acts, requirements and notifications have to be considered together, against the type of business, the location, and the nature of the project.

How this applies in practice

Buildings and construction projects — may require field noise measurement, noise propagation modelling, or a noise impact assessment report, in support of a construction permit, an Environmental Impact Assessment (EIA), or compliance with a regulator's conditions.

Factories and industrial estates — must meet the noise standards applicable to the type of business and the land use, and provide noise control measures or buffer zones to reduce the impact on surrounding communities.

Entertainment venues and temporary events — must comply with requirements on operating hours, permitted noise levels, measurement method and any conditions set by the local authority, and may also be assessed against their complaint history and their impact on the local community.

6. Compliance workflow and documentation

Whether the work is environmental noise, occupational health or building acoustics, the process generally follows the same sequence — from establishing which standards apply, through measurement, to reporting and follow-up — so that the data is credible, traceable, and usable as a basis for a decision or for demonstrating compliance.

1. Establish the context and the applicable requirements

Start by defining the type of work — environmental noise, occupational noise or building acoustics — so you can select the law, the standard, the measurement method, the indicators (LAeq, Lmax, dose, RT or STI) and the measurement period that match the purpose and the applicable requirements.

2. Plan the measurement

Set the measurement positions, microphone height, orientation, distance from reflecting surfaces, weather conditions and measurement duration, and configure the instrument parameters — frequency weighting (A, C or Z) and time weighting (Fast, Slow or Impulse) — in accordance with the referenced standard.

3. Calibrate and collect the data

Calibrate the meter before and after the measurement using a calibrator that is itself calibrated to standard, and record the calibration results and any drift found. Record the environmental conditions and any significant events during the measurement as well: this is the evidence that makes the result traceable and defensible if it is later disputed.

4. Analyse and assess

Analyse the data on sound technical principles and compare it against the applicable standard or requirement, taking measurement uncertainty and any other influencing factors into account, so that the conclusion is both accurate and credible.

5. Produce the report

The report should record the measurement in full: the objective, the method, the standards referenced, the instruments used, the calibration results, the measured results, the analysis, site photographs, a measurement position plan or noise map where relevant, and the conclusions and recommendations — so the data is traceable and can be used as technical or legal evidence.

6. Set corrective measures and follow up

Where results do not meet the requirement, analyse the cause and set appropriate controls — control at source, insulation or a noise barrier, changes to the work process, restricting the hours of the activity, or hearing protection in an occupational setting. Then re-test, to confirm that the measures have genuinely reduced the impact and that the requirement is now met.

7. Summary: context → metric → standard → documentation

FAQ

Should measurement and reporting use dBA or dBC?

It depends on the law, standard or requirement being referenced in each case. Where the requirement does not say otherwise, dBA is generally the primary indicator for noise impact assessment, because it most closely reflects how the human ear perceives sound.

However, where the source has pronounced low-frequency content — large air conditioning systems, generators, transformers, or sound systems with heavy bass — dBC should also be measured, or a frequency spectrum analysis carried out. A-weighting attenuates low frequencies, so relying on it alone gives an incomplete picture of the impact.

What should a good noise measurement report contain?

A complete report should contain at least the following:

• Instrument details: model, serial number and accuracy class
• Calibration information, and calibration results before and after the measurement
• The standards, measurement methods and requirements referenced
• Measurement positions, microphone height, and the conditions at each position
• Instrument settings, such as frequency weighting and time weighting
• Measurement results, statistics, and time-history graphs or data, including frequency spectrum analysis where relevant
• Site photographs, a measurement position plan, or a noise map where necessary
• Analysis of the results against the applicable criteria, with conclusions and recommendations

How do I know whether a project already complies?

A compliance assessment is not simply a question of whether the measured value “passes” or “fails”. The results have to be compared against the relevant law or standard, measurement uncertainty has to be taken into account, and the supporting documentation has to be complete.

A report that is traceable, states its measurement method clearly and carries complete supporting evidence will be credible, and can properly be used in an inspection, a complaint, or a regulator's process.

How can Geonoise help?

We measure and assess noise as an independent consultant: selecting the law, standards and measurement methods that are correct for your case, measuring with IEC 61672-1 Class 1 sound level meters calibrated by an ISO/IEC 17025 accredited laboratory, and producing a traceable report — with recommended control measures and a re-test to confirm the result.