Numerical Simulation ProjectNumerical Simulation Project

Numerical Simulation Project Numerical Simulation Project

University

of Parma

Numerical Simulation Numerical 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-Noise

FEMLAB) or V-Noise

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

Ramsete

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

response 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 IQSB

objective 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 microphones

of optimal locations for loudspeakers and microphones

Roadmap for numerical simulations Roadmap for numerical simulations

 Input / Output data flowsInput / Output data flows

Car Geometry

Car Geometry Acoustical Acoustical properties of properties of

materials materials

Behaviour of Behaviour of sound sources sound sources

Low-frequency Low-frequency FEM/BEM solver

FEM/BEM solver High-frequency High-frequency ray tracing ray tracing

Low-Frequency Low-Frequency Impulse Response Impulse Response

High-Frequency High-Frequency Impulse Response Impulse Response

Wide-band

Wide-band

Impulse Response

Impulse Response

Simulation Example - low frequencies Simulation 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 frequencies Simulation Example - high frequencies

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

In-situ measurement of the acoustical properties In-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 probe

Microflown pressure-velocity probe

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

 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 frequency

low frequency

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

 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 properties

both calibration and measurement of the acoustical properties

In-situ measurement of the loudspeaker radiation In-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 loudspeakers

acoustical pressure in front of the loudspeakers

Conclusions Conclusions

 Numerical simulation is nowaday workable in the whole frequency Numerical simulation is nowaday workable in the whole frequency range

range

 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 materials acoustical 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 result if 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.