Overview
ISO 15086-1:2001 - Hydraulic fluid power - Determination of the fluid-borne noise characteristics of components and systems - Part 1: Introduction provides the theoretical and practical foundation for characterizing fluid-borne noise in hydraulic systems. It introduces the transfer matrix approach and the frequency-domain methods used to describe pressure and flow ripples, wave propagation in pipes, and component impedance. The part applies to steady-state hydraulic circuits and sets out terms, symbols and measurement guidance to support quantitative hydro-acoustic analysis.
Key topics and technical requirements
- Frequency-domain representation: Pressure and flow ripples are modelled as Fourier series (fundamental frequency and harmonics). Emphasis on periodic signals for noise characterization.
- Transfer matrix theory: Uses complex coefficients to relate pressure and flow at different points in a piping system, providing a basis to determine component and system behaviour.
- Wave propagation in pipes: Plane-wave modelling accounts for fluid viscosity and computes coefficients (A, B) that depend on pipe geometry, acoustic velocity and fluid properties; applicable to Newtonian fluids.
- Impedance and admittance: Defined as the complex ratio of pressure ripple to flow ripple at each harmonic. Local and characteristic impedance concepts are used to describe energy transmission and reflection.
- Continuity at junctions: Algebraic summation of flow at pipe junctions and methods to infer pressure/flow at other locations using transfer relationships.
- Measurement guidance:
- Pressure ripple: Piezoelectric pressure transducers recommended for adequate bandwidth.
- Flow ripple: No direct broadband flow sensors currently standardized - flow is normally inferred from two pressure measurements combined with transfer-matrix coefficients.
- Terms and symbols: Standardizes vocabulary (cross-referenced to ISO 5598) and a comprehensive symbol set for frequency-domain analysis.
Practical applications
ISO 15086-1 is used to:
- Guide acoustic characterization and reduction of hydraulic machine noise.
- Support design and testing of quieter hydraulic components and systems (pumps, valves, pipelines).
- Provide test-lab procedures for measuring pressure ripple and inferring flow ripple for component datasheets.
- Help system integrators and OEMs assess hydro-acoustic energy paths and specify mitigation (dampers, pipeline routing, component selection).
Typical users include hydraulic designers, acoustical engineers, test laboratories, component manufacturers, and researchers in fluid power noise control.
Related standards
- ISO 15086-2: Measurement of the speed of sound in a fluid in a pipe (companion part).
- ISO 5598: Fluid power systems and components - Vocabulary (normative reference).
- Prepared by ISO/TC 131 (Fluid power systems), Subcommittee SC 8 (Product testing).
Keywords: ISO 15086-1, hydraulic fluid power, fluid-borne noise, pressure ripple, flow ripple, transfer matrix, impedance, hydro-acoustic energy, piezoelectric transducer.