| 📋 Article Summary — Noise Specifications for Plant and Equipment Purchase | |
|---|---|
| Key Fact 1 | Sound power level (LW, in dB(A)) is the correct metric for comparing machines — not sound pressure level (which varies with distance and environment) |
| Key Fact 2 | WHS Regulations require noise consideration in plant design and procurement — specifying noise performance is a legal obligation, not optional |
| Key Fact 3 | Retrofitting noise controls to existing machinery costs 5–10× more than specifying equivalent noise reduction at the design stage |
| Read Time | 8 min |
The Most Cost-Effective Noise Control: Getting It Right at Purchase
The single most cost-effective opportunity to control workplace noise is at the equipment procurement stage. Once a noisy machine is installed and in production, retrofitting adequate noise controls is technically difficult and expensive — often costing 5–10 times the price of equivalent noise reduction designed into the machine from the beginning. A brief specification requirement added to a capital equipment purchase contract can prevent years of noise overexposure and engineering remediation costs.
Legal Obligations for Noise in Plant Design and Procurement
Under the WHS Regulations 2017, plant designers and manufacturers have duties to design and manufacture plant that, when used for its intended purpose, does not pose a risk to health and safety, including noise risks. PCBUs that import, supply, or use plant also have obligations. When purchasing plant and equipment, PCBUs should:
- Request noise emission data from suppliers before purchase
- Include noise performance requirements in purchase specifications
- Verify compliance with stated noise levels before accepting delivery
Sound Power Level vs Sound Pressure Level: What to Specify
Two noise metrics appear in equipment specifications, and confusing them leads to poor purchase decisions:
- Sound pressure level (SPL, Lp): The noise level measured at a specific distance from the machine in a specific environment. SPL varies with distance and room acoustics — it tells you what noise level an operator hears if they stand at a specified position, but cannot be used to compare machines in different environments.
- Sound power level (LW, also written as Lw or SWL): A fundamental property of the machine’s noise emission, independent of distance and environment. Sound power is the total acoustic energy radiated by the machine. Once you know the sound power level, you can calculate the expected sound pressure level at any distance in any environment using standard acoustic equations.
Sound power level is the correct metric to specify in purchase contracts. It must be measured and reported according to ISO 3744, ISO 3745, or equivalent standards. The declaration should state the uncertainty (±dB) associated with the measurement.
Practical Noise Purchase Specification Requirements
A noise performance specification clause for machinery procurement should include:
- Maximum declared sound power level (LWA) in dB(A) re 1 pW
- Maximum operator position sound pressure level (LpA) in dB(A) at [specified distance] under [specified operating conditions]
- Reference to the measurement standard used (ISO 3744, ISO 3745, or relevant product-specific standard)
- Requirement for third-party verification of noise data (not just manufacturer’s own test)
- Acceptance testing clause — the right to measure noise on delivery and reject plant that does not meet specification
- Warranty covering noise performance — supplier responsible for remediation if specified noise levels are not achieved in situ
The “Buy Quiet” Principle
Safe Work Australia’s “buy quiet” initiative encourages PCBUs to include noise performance as a mandatory purchase criterion alongside conventional purchase factors such as cost, productivity, and maintenance. In practice, this means:
- Adding noise performance as a weighted criterion in equipment tenders
- Requesting noise comparison data when evaluating competing equipment models
- Including noise measurements in pre-purchase trials and site demonstrations
- Requiring that demonstration machines reflect production specification, not specially quietened prototypes
Frequently Asked Questions
A supplier claims their machine is “quiet” — how do I verify this before purchase?
Request the formally measured sound power level (LWA) data to ISO 3744 with the measurement uncertainty and test conditions stated. Ask for the test report, not just the claimed value. If the supplier cannot provide third-party verified noise data, consider whether the “quiet” claim is credible. For high-value equipment, a pre-purchase demonstration with an independent noise measurement by a NATA-accredited occupational hygienist provides definitive pre-purchase verification.