Powertrain NVH

Noise, Vibrations, Harshness

MOT/ACMOT-E

Who should attend?

  • This course provides a deeper knowledge and competencies of the nature and origin of noises and vibrations generated in the powertrains and the measurement and analysis methods used in the vibro-acoustic field. it aims at implementing technical solutions to reduce noise and vibration.
Audience :
  • Engineers and technical staff from engine design or testing involved in vibration physics on noise aspect as well as mechanical behavior.

Level : Advanced

Course Content

  • Acoustic & vibrations in the industrial world

      • Acoustics: pressure, intensity, sound power; levels expressed in decibels, sound level structure; sound velocity.
      • Time and space variations of waves, plane and spherical waves, propagation law. Human ear, hearing properties, ear sensitivity, A-weighting decibel levels. Vibration parameters analysis: acceleration, velocity, displacement.
      • Free or forced response ringing oscillator, free-running frequency, role of damping.
  • Signal analysis instruments & methods

      • Signals classification and processing; fast Fourier transformation (FFT): sampling, weigh time space, spectrum.
      • Time analysis, spectral analysis, white noise, pink noise, order analysis.
      • Tri-dimensional representations, sonograms, time-frequency representations.
      • Acoustic phenomena measure instruments: microphones, displacement sensors, acceleration sensors, acoustic imaging, anechoic bench.
      • Modal analysis (experimentations): vibration mode of a metal plate; structure response to a dynamic stress (loudspeaker, vibrator, unbalanced electric engine); deformation display with a stroboscope.
  • Powertrain noise vibration & harshness

      • Powertrain dynamic behavior: internal forces of inertia and combustion, effect of parts deformation, deformation of powertrain structures, finite element modeling, main modes of resonance.
      • Powertrain acoustic radiation. Radiating envelopes. Excitations sources. Acoustic power. Powertrains vibration transfers. Structures and effects of housings of powertrain.
      • Efforts of inertia: single-cylinder, three and four cylinder in-line engines dynamics; use of balancer shafts; composition of the combustion and inertia efforts; effect of dual mass flywheel (DMA).
      • Combustion noise: cylinder pressure, dynamic pressure, spectral analysis of the cylinder pressure; technologies impact on the combustion noise; transfer and spread of combustion noise; measurement of combustion noise; combustion noise in transient operation.
  • Powertrain main noises & vibrations

      • Injection systems: technical description of the systems, acoustic phenomena related to the operation of the system, mechanisms of noise generation in medium and high frequency, fluid-structure interaction, effect of dispersion and drift, analysis of the measured signals.
      • Piston slap: play liaison of the moving parts, piston slap, noise analysis.
      • Sounds training distribution: the whining, scraping, rubbing belt, role of the housings; origins and solutions.
      • Whistle of the turbocharger: meow, sound of wind and sound of discharge; origins and solutions.
      • Noise of gearboxes: whining, hoarse sound; origins and solutions.
      • Aerodynamic noise: noise related to filling air and exhaust.
  • Acoustic signatures of the powertrain (PT) main sources

      • Acoustic and vibratory process during design: reduction at source or vibration filtration.
      • PT primary and secondary sources, glossary of the engine’s main sources.
      • Examples of acoustic signatures (analysis from sonograms): diesel injector, supercharger, timing, belt-driven accessories, gearbox, starter, intake noise.
      • Demonstrator: analysis of the noise sources of an electrically-driven thermal engine model; spectral analysis during a speed increase, interpretation.
  • Parts mechanical resistance to vibrations

      • Validation of engine parts with all the vibration types: identifying the frequencies and the rates of generation of overvoltage and resonances, quantification of vibratory levels during acceleration and displacement, determining the endurance conditions and durations.
      • Examples: validation of an intake P/T sensor, of an oil gauge guide, of an oil turbo pipe.

Learning Objectives

  • Upon completion of the course, participants will be able to:
  • know the parameters used to characterize noise and vibrations,
  • understand vibrating systems behaviors and control parameters,
  • know the signal processing instruments and methods,
  • master experimental techniques,
  • identify the acoustic signature of the powertrain’s (PT) main sources,
  • interpret the sonograms corresponding to the main vibration sources of the powertrain,
  • carry out a validation test on vibration for engine-related parts.

Ways & Means

  • Real and concrete examples of powertrain vibro-acoustic problems discussed by experts from the automotive world. Real and concrete solutions implemented in the industry.