ISO 6798-2:2020

Overview

ISO 6798-2:2020 - "Reciprocating internal combustion engines - Measurement of sound power level using sound pressure - Part 2: Survey method" specifies a standardized survey method to measure the sound power level of reciprocating internal combustion engines using sound pressure on an enclosing measurement surface. It applies to engines covered by ISO 3046‑1 and other internal combustion engines where no specific international standard exists. The survey method delivers an A-weighted sound power result with accuracy grade 3 and results rounded to 0.1 dB.

Key technical topics and requirements

• Scope and intent: Defines a survey (simpler) measurement approach within the ISO 6798 series for engine noise characterization.
• Test environment: Requirements for an indoor room or flat outdoor area that is adequately isolated from background noise and meets acoustic qualification criteria (acoustic adequacy and background-noise limits).
• Instrumentation and calibration: Specifies acceptable instrumentation classes (survey method permits Class 2 sound level meters/filters and Class 1 calibrators) and calibration procedures in line with IEC/ISO references.
• Installation and operating conditions: Clear rules for engine installation, auxiliaries and operating conditions during measurement (referenced to ISO 3046 series).
• Measurement method: Defines measurement surface geometry, measurement distance, microphone positions, and the use of a reference box when required.
• Corrections and calculations: Procedures for background-noise correction (formula-based), environmental correction, calculation of surface time‑averaged sound pressure levels and final sound power level.
• Uncertainty and acceptance criteria: Survey-grade measurement uncertainty values are provided (A-weighted standard deviation of reproducibility = 3.0 dB). Typical criteria: background noise difference ΔL ≥ 3 dB, background correction K ≤ 3.0 dB, microphone position standard deviation sL ≤ 2 dB.
• Reporting and record keeping: Required test data, measurement conditions and test report structure are specified.

Practical applications

• Characterizing and comparing engine acoustic radiation for design or procurement
• Comparative and acceptance testing against contractual noise limits
• Baseline surveys to inform noise-control engineering and mitigation
• Predicting sound pressure levels in the operating environment using sound power results
• Supporting compliance assessment, product documentation and noise labeling

Who should use ISO 6798-2:2020

• Engine manufacturers and R&D teams
• Acoustical engineers and test laboratories
• Suppliers, installers and end users specifying noise limits
• Regulatory and certification bodies performing engine noise surveys

Related standards

• ISO 6798-1 (engineering method)
• ISO 3046-1 / ISO 3046-3 (engine performance and test methods)
• ISO 3746 / ISO 3744 (sound power determination methods)
• IEC 61672-1, IEC 60942, ISO 6926 (instrumentation and calibration)

Keywords: ISO 6798-2:2020, reciprocating internal combustion engines, sound power level, survey method, sound pressure, engine noise measurement, acoustic testing.