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Numerical Simulation Project

University of Parma. Numerical Simulation Project. Numerical Simulation. FEM/BEM modelling at low frequency (< 500 Hz) with COMSOL (ex FEMLAB) or V-Noise Pyramid Tracing modelling at high frequency (> 500 Hz) with Ramsete

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Numerical Simulation Project

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  1. University of Parma Numerical Simulation Project

  2. Numerical Simulation • FEM/BEM modelling at low frequency (< 500 Hz) with COMSOL (ex FEMLAB) or V-Noise • Pyramid Tracing modelling at high frequency (> 500 Hz) with Ramsete • The low-frequency response is converted into an impulse response by employing an IFFT • Of consequence, the result of the simulation can be assessed by objective rating employing AQT and/or IQSB • The sound inside the simulated car can also be listened to, employing the auralization technique (convolution with the simulated impulse responses) • The goal is to evaluate the design of car interiors, which should not only be optinized for low noise, but also for easy speech communication among the passengers, optimal behaviour of the sound system, and correct operativity of handsfree telephone systems. • The feedback can drive the design of car interiors, and the choice of optimal locations for loudspeakers and microphones

  3. Roadmap for numerical simulations • Input / Output data flows Car Geometry Acoustical properties of materials Behaviour of sound sources Low-frequency FEM/BEM solver High-frequency ray tracing Low-Frequency Impulse Response High-Frequency Impulse Response Wide-bandImpulse Response

  4. Simulation Example - low frequencies Results_: Complex Frequency Response, which can be exported and transformed back to an impulse response thanks to an inverse FFT

  5. Simulation Example - high frequencies Results_: Impulse Response and Frequency Response

  6. In-situ measurement of the acoustical properties • The measurement of the acoustical impedance is performed employing a Microflown pressure-velocity probe

  7. In-situ measurement of the acoustical properties • The probe needs to be calibrated for proper gain and phase matching at low frequency Calibration over a reflecting surface Free-Field calibration

  8. In-situ measurement of the acoustical properties • A specific software (Aurora plugin) has been developed for speding up both calibration and measurement of the acoustical properties Input parameters Results

  9. In-situ measurement of the loudspeaker radiation • The probe can also be used for mapping the particle velocity and the acoustical pressure in front of the loudspeakers

  10. Conclusions • Numerical simulation is nowaday workable in the whole frequency range • Modern program are fast and reliable - the great effort is still about drawing the 3D CAD model and assigning suitable values of the acoustical properties of materials • It is now possible to measure “in situ” the acoustical impedance of the surfaces inside a car, thanks to the microflown pressure-velocity probe. • The results can be converted in an impulse response, which can be saved in standard WAV format and can be processed exactly as if it was an experimental result • Advanced evaluation method are now available for evaluating the perceived sound quality (AQT, IQSB) • The results can even be employed for auralization of the response of the sound system in the car, allowing for subjective listening tests before the first prototype are even built.

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