Overview
ISO 4412-3:1991 - "Hydraulic fluid power - Test code for determination of airborne noise levels - Part 3: Pumps - Method using a parallelepiped microphone array" is an ISO test code for measuring the airborne noise (sound power) radiated by hydraulic pumps (and optionally motors) under controlled conditions. Published in 1991, this part complements ISO 4412-1/2 by allowing simpler, lower-cost pump mounting and drive arrangements in an anechoic chamber while still producing engineering-accurate results for A-weighted and one-third octave band measurements (typical frequency range 100 Hz–10 000 Hz).
Key topics and technical requirements
- Test environment: Measurements are performed in an anechoic or quasi-free-field room that provides free-field conditions over two mutually perpendicular reflecting planes; environmental corrections and calibration follow ISO 3744 procedures.
- Measurement uncertainty: Engineering methods from ISO 3744 aim for standard deviations similar to tabled values; A‑weighted sound power is typically determined with about ±2 dB uncertainty.
- Instrumentation: Acoustic instrumentation must comply with IEC 651 (sound level meters) and ISO 3744 performance/calibration; fluid and mechanical measurements use industrial “class” accuracy.
- Installation & mounting: Pump mounting should minimize structure-borne noise; flexible drives or isolated motors are used so the drive is outside the test space. Hydraulic lines, filters and cooling devices must reflect normal operating configuration.
- Operating limits: Controlled parameters (flow, pressure, speed) are maintained within narrow tolerances (typically ±2%) and temperature within ±2 °C during tests.
- Microphone array & measurement points: A parallelepiped microphone array of six microphones is used (coordinates and array geometry specified). A reference box (smallest rectangular parallelepiped enclosing the pump) defines the measurement surface.
- Background noise & corrections: Background levels must be sufficiently below pump levels (generally ≥6 dB); ISO 3744 correction methods apply.
- Calculation & reporting: Surface sound pressure levels and sound power are calculated per ISO 3744; required test data and reporting fields are specified.
Applications and users
- Pump and hydraulic component manufacturers for product development, benchmarking and quality control.
- Acoustic test laboratories and OEM test facilities validating pump sound power levels.
- Design and R&D engineers assessing noise performance and mitigation measures.
- Regulatory or procurement teams requiring standardized acoustic data for component selection.
Related standards
- ISO 4412-1: Pumps (general test methods)
- ISO 4412-2: Motors (related methods)
- ISO 3744: Acoustics - determination of sound power levels (methodology and environment)
- IEC 651: Sound level meters
- ISO 5598: Fluid power vocabulary
Keywords: ISO 4412-3:1991, hydraulic fluid power, pump noise testing, airborne noise, parallelepiped microphone array, anechoic chamber, sound power level, ISO 3744, IEC 651.