Overview
EN 27574-4:1988 (ISO 7574-4:1985) - published by CEN/ISO - defines statistical methods to determine and verify a labelled noise emission value for batches (lots) of machinery and equipment. It gives labellers guidelines to set a stated (labelled) upper noise value and specifies sampling procedures to check whether a lot complies with that value. The standard assumes noise emission values in a batch are approximately normally distributed and requires a specified reference standard deviation for verification. It does not cover the consequences or corrective actions if a lot fails verification.
Key topics and requirements
- Purpose: Determine and verify a labelled (upper) noise emission value for batches of machines.
- Assumptions: Noise values ≈ normal distribution; verification uses a reference standard deviation (σM).
- Risk/acceptance basis: Procedures are designed so that a lot with at most 6.5% of items exceeding the labelled value has approximately 95% probability of acceptance (producer’s risk point).
- Labelled-value guidance: Labellers are given formulae to set the labelled value (Lc) relative to measured mean and σM (examples and equations provided in the standard).
- Sampling procedures: Three equivalent inspection methods are specified - single sampling, double sampling, and sequential sampling - each requiring a prescribed sample size and accept/reject criteria (using operating-characteristic concepts).
- Reference information: Annexes include operating-characteristic curves, examples and guidance for estimating standard deviations and using OC curves.
- Scope limits: Focuses on checking an upper limit only (one-sided). It does not prescribe actions after non-conformance.
Practical applications and users
Who uses this standard:
- Manufacturers and labellers of mass-produced machinery and equipment who must declare noise emission values on labels or in documentation.
- Testing laboratories and quality departments performing batch verification of noise emissions.
- Certification bodies and regulators designing labelling codes or verification procedures for specific machine families.
Practical uses:
- Setting a defensible, statistically based labelled noise limit for product families.
- Designing sampling plans to verify compliance of lots with declared noise values.
- Integrating verification rules into an organizational noise-labelling code (the code must specify σM, sampling method and sample sizes).
Related standards
- ISO 7574-1 (general considerations and definitions)
- ISO 3951 (sampling by variables - referenced procedure)
- ISO 4871 (noise labelling of machinery and equipment)
- EN 27574-4 is identical in content to ISO 7574-4:1985 and contains annexes with OC curves and symbol lists for practical implementation.
Keywords: acoustics standard, noise emission, machinery noise, statistical sampling, labelled value, batch verification, ISO 7574-4, EN 27574-4, sampling inspection, operating characteristic.
