CEN ISO/TS 7849-2:2022

Overview

CEN ISO/TS 7849-2:2022 (identical to ISO/TS 7849-2:2009) specifies an engineering method for determining the airborne sound power levels emitted by machinery using surface vibration measurements. The Technical Specification covers procedures to convert measured vibratory velocity on machine surfaces into an estimate of airborne sound power, including the determination of the machine‑specific radiation factor (ε) across frequency bands. This method applies only to noise radiated by vibrating solid surfaces - not aerodynamic noise - and is intended for stationary processes.

Key topics and technical requirements

• Principle: Airborne sound power from structure-borne radiation is assumed proportional to the mean square normal component of surface velocity and to the vibrating surface area.
• Instrumentation and calibration: Requirements for vibration transducers (contact and non‑contact), amplifiers, filters, integrators and calibration procedures.
• Installation and operating conditions: Guidance on machine description, mounting, operating states and environmental considerations to ensure reproducible measurements.
• Measurement procedure: Selection and number of measurement positions, mounting of transducers, corrections for extraneous vibratory velocity and averaging to determine mean vibratory velocity level.
• Radiation factor determination: Methods to determine the frequency‑dependent radiation factor specific to the machine under test (ε), rather than assuming ε = 1 (upper bound).
• Calculations: Steps to compute airborne sound power from vibratory data, including octave/one‑third‑octave band processing and conversion to A‑weighted levels where required.
• Measurement uncertainty: Guidance and informative annex on estimating uncertainty and reporting results.
• Annexes: Informative and normative annexes provide practical guidance - e.g., frequency band recommendations, converting acceleration to velocity, and A‑weighting procedures.

Applications and users

This standard is especially useful when direct airborne methods (e.g., ISO 3746, ISO 3747, ISO 9614) are impractical because of:

• High background noise or acoustic reflections
• Need to separate structure‑borne noise from aerodynamic noise
• Measurement of individual components or subassemblies within noisy environments

Typical users:

• Acoustical consultants and test laboratories
• Noise control and mechanical engineers (OEMs)
• R&D teams and product designers assessing machine noise sources
• Compliance managers documenting machine noise performance

Related standards

• ISO/TS 7849-1 (survey method using fixed radiation factor)
• ISO 3746, ISO 3747 (direct airborne sound power measurement)
• ISO 9614 (sound intensity methods)

Keywords: airborne sound power, vibration measurement, radiation factor, machinery noise, sound power level, vibration transducer, measurement uncertainty, acoustics standard.