numerical simulation project

Numerical Simulation ProjectNumerical Simulation Project

Universityof Parma

|| Page 218.05.200618.05.2006 Angelo FarinaAngelo Farina UNIPR / ASK IndustriesUNIPR / ASK Industries || A All Rights Reservedll Rights Reserved || ConfidentialConfidential

Numerical SimulationNumerical Simulation

FEM/BEM modelling at low frequency (< 500 Hz) with COMSOL (ex FEM/BEM modelling at low frequency (< 500 Hz) with COMSOL (ex FEMLAB) or V-NoiseFEMLAB) or V-Noise

Pyramid Tracing modelling at high frequency (> 500 Hz) with Pyramid Tracing modelling at high frequency (> 500 Hz) with RamseteRamsete

The low-frequency response is converted into an impulse The low-frequency response is converted into an impulse response by employing an IFFTresponse by employing an IFFT

Of consequence, the result of the simulation can be assessed by Of consequence, the result of the simulation can be assessed by objective rating employing AQT and/or IQSBobjective rating employing AQT and/or IQSB

The sound inside the simulated car can also be listened to, The sound inside the simulated car can also be listened to, employing the auralization technique (convolution with the employing the auralization technique (convolution with the simulated impulse responses)simulated impulse responses)

The goal is to evaluate the design of car interiors, which should The goal is to evaluate the design of car interiors, which should not only be optinized for low noise, but also for easy speech not only be optinized for low noise, but also for easy speech communication among the passengers, optimal behaviour of the communication among the passengers, optimal behaviour of the sound system, and correct operativity of handsfree telephone sound system, and correct operativity of handsfree telephone systems.systems.

The feedback can drive the design of car interiors, and the choice The feedback can drive the design of car interiors, and the choice of optimal locations for loudspeakers and microphonesof optimal locations for loudspeakers and microphones


Roadmap for numerical simulationsRoadmap for numerical simulations

Input / Output data flowsInput / Output data flows

Car GeometryCar Geometry Acoustical Acoustical properties of properties of

materialsmaterials

Behaviour of Behaviour of sound sourcessound sources

Low-frequency Low-frequency FEM/BEM solverFEM/BEM solver

High-frequency High-frequency ray tracingray tracing

Low-Frequency Low-Frequency Impulse ResponseImpulse Response

High-Frequency High-Frequency Impulse ResponseImpulse Response

Wide-bandWide-bandImpulse ResponseImpulse Response


Simulation Example - low frequenciesSimulation Example - low frequencies

Results_: Complex Frequency Response, which can be exported and transformed back to an impulse response thanks to an inverse FFT


Simulation Example - high frequenciesSimulation Example - high frequencies

Results_: Impulse Response and Frequency ResponseResults_: Impulse Response and Frequency Response


In-situ measurement of the acoustical propertiesIn-situ measurement of the acoustical properties

The measurement of the acoustical impedance is performed employing a The measurement of the acoustical impedance is performed employing a Microflown pressure-velocity probeMicroflown pressure-velocity probe



The probe needs to be calibrated for proper gain and phase matching at The probe needs to be calibrated for proper gain and phase matching at low frequencylow frequency

Calibration over a reflecting surfaceCalibration over a reflecting surface Free-Field calibrationFree-Field calibration



A specific software (Aurora plugin) has been developed for speding up A specific software (Aurora plugin) has been developed for speding up both calibration and measurement of the acoustical propertiesboth calibration and measurement of the acoustical properties

Input parametersInput parameters ResultsResults


In-situ measurement of the loudspeaker radiationIn-situ measurement of the loudspeaker radiation

The probe can also be used for mapping the particle velocity and the The probe can also be used for mapping the particle velocity and the acoustical pressure in front of the loudspeakersacoustical pressure in front of the loudspeakers


ConclusionsConclusions

Numerical simulation is nowaday workable in the whole frequency Numerical simulation is nowaday workable in the whole frequency rangerange

Modern program are fast and reliable - the great effort is still about Modern program are fast and reliable - the great effort is still about drawing the 3D CAD model and assigning suitable values of the drawing the 3D CAD model and assigning suitable values of the acoustical properties of materialsacoustical properties of materials

It is now possible to measure “in situ” the acoustical impedance of It is now possible to measure “in situ” the acoustical impedance of the surfaces inside a car, thanks to the microflown pressure-the surfaces inside a car, thanks to the microflown pressure-velocity probe.velocity probe.

The results can be converted in an impulse response, which can The results can be converted in an impulse response, which can be saved in standard WAV format and can be processed exactly as be saved in standard WAV format and can be processed exactly as if it was an experimental resultif it was an experimental result

Advanced evaluation method are now available for evaluating the Advanced evaluation method are now available for evaluating the perceived sound quality (AQT, IQSB)perceived sound quality (AQT, IQSB)

The results can even be employed for auralization of the response The results can even be employed for auralization of the response of the sound system in the car, allowing for subjective listening of the sound system in the car, allowing for subjective listening tests before the first prototype are even built.tests before the first prototype are even built.

numerical simulation project

Documents

angelo farinaunipr

frequency response page

high frequency

complex frequency response

loudspeakers page

microphones page

impulse response thanks

acoustical pressure