Overview
ISO/TS 7849-1:2009 - "Acoustics - Determination of airborne sound power levels emitted by machinery using vibration measurement - Part 1: Survey method using a fixed radiation factor" defines a reproducible survey method to estimate an upper limit for the A-weighted airborne sound power (LWA,max) produced by machinery when that sound is generated by vibrating solid surfaces. The method assumes a fixed A‑weighted radiation factor (εA = 1) and is intended for cases where direct airborne noise measurements are impractical (for example, high background noise) or where the structure‑borne component of noise needs to be separated from aerodynamic sources.
Key topics and requirements
- Scope and limitations
- Applies only to structure vibration generated sound (not aerodynamic noise).
- Best suited for stationary processes and for machinery whose radiation behavior is not dominated by small localized sources.
- Measurement principle
- Relates the machine’s A‑weighted vibratory velocity (normal component, averaged over a defined surface) and surface area to an upper bound of airborne sound power using a fixed radiation factor.
- Instrumentation and calibration
- Requirements for vibration transducers, including non‑contacting sensors, amplifiers, integrators and calibration procedures.
- Guidance on mounting and use of accelerometers/vibrometers per ISO/5348 recommendations.
- Test setup and procedure
- Machine description, installation and defined vibrating measurement surface.
- Number and location of measurement positions, environmental condition checks, and measurement sequence.
- Calculations and uncertainty
- Procedures to compute the mean A‑weighted vibratory velocity level and the resulting upper limit A‑weighted airborne sound power level (LWA,max).
- Annex guidance on estimating measurement uncertainty (referencing ISO/IEC Guide 98-3, GUM).
Applications and users
- Practical uses
- Rapid survey assessments of machinery noise when direct sound power methods (ISO 3746, ISO 3747, ISO 9614) are infeasible due to background noise or reflections.
- Distinguishing the structure-borne component from aerodynamic noise.
- Comparative screening of similar machine families or identifying vibration‑driven noise sources on assemblies.
- Primary users
- Acoustical engineers, noise consultants, test laboratories, machinery manufacturers, R&D teams and regulatory agencies conducting noise compliance screening or diagnostic investigations.
Related standards
- ISO 3746, ISO 3747 - airborne sound power determination (direct methods)
- ISO 9614 (all parts) - sound intensity measurement
- ISO 5348 - mounting of accelerometers
- IEC 61672-1 - sound level meter specifications
- ISO/IEC Guide 98-3 (GUM) - uncertainty of measurement
Keywords: ISO/TS 7849-1:2009, acoustics standard, airborne sound power, vibration measurement, A-weighted, radiation factor, machinery noise, structure-borne noise, survey method, measurement uncertainty.