Overview
ISO 6798-1:2020 - "Reciprocating internal combustion engines - Measurement of sound power level using sound pressure - Part 1: Engineering method" - defines an engineering-grade procedure to measure the sound power level of reciprocating internal combustion engines using measured sound pressure on an enveloping surface. It applies to engines covered by ISO 3046-1 and other internal combustion engines where no specific international standard exists. The method is intended for accuracy Grade 2 measurements and supports both A-weighted and frequency-band sound power results.
Key technical topics and requirements
- Scope and applicability: Applies to reciprocating internal combustion engines (as defined by ISO 3046-1) and analogous engines lacking other standards.
- Test environment: Criteria for background noise and acoustic adequacy of the test environment are specified (free-field over a reflecting plane conditions are assumed for this method).
- Instrumentation: Recommendations for high-accuracy instrumentation (Class 1 sound level meters, filters and calibrators) and calibration procedures.
- Installation & operating conditions: Defined installation, engine condition, and operating conditions to ensure reproducible, comparable results.
- Measurement procedure: Guidance on measurement distance, measurement surface and area, microphone positions and reduction criteria for microphone counts.
- Corrections & calculation:
- Background noise correction (formula-based)
- Environmental corrections and surface time-averaged sound pressure calculations
- Calculation of sound power level from measured pressure data
- Uncertainty and accuracy:
- Measurement results are rounded to the nearest 0.1 dB
- Table of reproducibility upper-bound standard deviations per octave/one-third-octave band (example: A-weighted reproducibility ~1.5 dB for ISO 6798‑1)
- Reporting: Required test data, information to be recorded, and test report contents are specified.
- Normative annexes: Qualification procedures for acoustic environments, calculation methods for A-weighted levels from frequency bands, and reference meteorological conditions.
Practical applications
- Characterizing and validating engine noise emission for design, procurement and compliance
- Comparing radiation noise between different engine models or installations
- Supporting engineering noise control measures (source reduction, enclosure design)
- Predicting sound pressure at receiver positions based on measured sound power
- Providing standardized test data for contract specifications, certification, and product literature
Who should use this standard
- Engine manufacturers and acoustic test laboratories
- Acoustic and mechanical engineers involved in engine noise control
- Regulatory bodies and certification agencies
- Procurement teams specifying noise requirements in contracts
- Installers and integrators evaluating expected radiated noise
Related standards
Keywords: ISO 6798-1, sound power level, reciprocating internal combustion engines, engineering method, sound pressure measurement, acoustic measurement, measurement uncertainty.
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