ISO 7574-3:1985

Overview

ISO 7574-3:1985 is part of the ISO 7574 series on acoustics and provides a simple (transition) statistical method for determining and verifying stated noise emission values for batches (lots) of machinery and equipment. It is intended as guidance for labellers and testers when a specific noise labelling code for a family of machines does not yet exist. The method is compact and designed for reproducibility conditions, with practical guidance on sampling and decision rules.

Key Topics

• Scope and intent: Guidance for labellers to determine a labelled value and for testing laboratories to verify that a batch conforms to that value. The part does not address contractual consequences if verification fails.
• Measurement basis: Measurements must follow the specific measurement test code for the machine family; if none exists, ISO 3741, ISO 3742, ISO 3743, ISO 3744 or ISO 3745 may be used with clearly stated installation and operating conditions.
• Sample size and sampling: A sample size of n = 3, taken at random from the batch, is recommended as the simple transition approach. Measured values should be recorded without rounding prior to statistical calculations.
• Labelled value calculation: The labelled value is derived by adding a positive constant K to the sample mean (E*): labelled value = E* + K. The labeller determines K based on the definition of the labelled value; guidance indicates K should be >= 5 dB.
• Reference variability: A reference total standard deviation of sigma = 3.5 dB is given for guidance. If the actual total standard deviation differs, ISO 7574-4 provides more detailed procedures.
• Decision rule for verification: Using the sample mean E*, the rule in the standard is:
  • If E* < labelled value - 2 dB, the labelled value is confirmed for the batch.
  • If E* > labelled value - 2 dB, the labelled value is not confirmed for the batch.

Applications

• Product labelling: Establishing conservative, verifiable noise labels for batches during a transition to a formal labelling code.
• Quality control: Quick batch verification in manufacturing or pre-shipment inspection where a simple statistical approach is preferred.
• Contractual agreements: Use by agreement between suppliers and purchasers when no specific industry code exists; installation and operating conditions must be clearly stated.

Related Standards

• ISO 7574-1 - General considerations and definitions for the ISO 7574 series.
• ISO 7574-4 - Methods for stated values for batches; further guidance on sample size and variability.
• ISO 3741, ISO 3742, ISO 3743, ISO 3744, ISO 3745, ISO 3746 - Measurement test codes and sound power determination methods referenced for testing procedures.

Practical note: ISO 7574-3 is intended as a transitional, guidance-level procedure. For permanent labelling codes or where tighter statistical control is required, use the appropriate ISO 7574 part or an agreed industry measurement code.