Researches and Applications for Automotive Field Andrea Azzali, Eraldo Carpanoni, Angelo Farina University of Parma

Topics University of Parma Main Researches: Objective evaluation index for audio performance characterization and Innovative Analysis technique for musical signal (AQT system) Virtual car cockpit for system comparison Algorithm for audio equalization (AQT, CTC) Simulation of digital system staying inside car cockpit Robust measuring technique for reliable and stable characterization with IR

University of Parma Innovative dynamic analysis technique AQT Tool

University of Parma Goal : Substitute classical analysis based on FFT with dynamic analysis Reasons: FFT characterize system only in steady state condition BUT Hearing system is more sensible vs transient Musical signal is not a steady state signal Solution: Aqt analysis system Innovative dynamic analysis technique

University of Parma Features: Use transient stimulus instead steady-state ones Find psychoacoustics response more closed to real perceived curve than FFT response Find resonance in cockpit and tail that affect hearing Useful during car system development Output: Articulation parameter Energy deviation from best curve corresponding to pleasant hearing inside the car AQT Analysis system

University of Parma Objective evaluation system Evaluation Test

Objective evaluation system University of Parma Activity in Collaboration with CRF: Fiat Research Centre Goal: Reduce time needed for system characterization during car system development Obtain Reliable characterization of hearing inside the car and develop a series of objective parameter useful as project statement Status: In progress (deadline 24/12/2003)

Objective evaluation system Proceeding: Study of main features that affect subjective evaluation of car system >> OUTPUT: Subjective Index of performance (New IPA) Study of a series of objective parameter able to describe this features >> OUTPUT: statement Study of correlation between subjective and objective parameter >> OUTPUT: Objective Index of Performance University of Parma

Objective evaluation system University of Parma Subjective evaluation parameters: Intensity of Sound and SPL MAX. Distortion. Spectral attributes. Spatial attributes. Speech clarity and intelligibility. Low frequency quality. Articulation and clarity of sound (Fidelity) Objective Parameters Dynamic response of car inside (AQT Method) Articulation and energy recovery at low frequency (AQT) Spatial parameter (IACC and localization index) Speech clarity (STI) ……..

Objective evaluation system Current activities: Preparation of subjective test based on questionnaire developed for subjective database and statistical process Study of listening room as standard listening test environment instead of car inside University of Parma

Virtual listening system University of Parma Listening room

Virtual listening system Goal: Fast comparison between different car audio system Detailed highline of difference Reasons: The tests not be done in the car because of the high switching time and the unavailability of the car after long time. Features: Fast switch between different configurations Capability of comparison by audio system of the cars nevermore available The listening room reproduce the binaural recorded tracks in the car and doesnt insert any apparent alteration. University of Parma

Virtual listening system Proceeding: Record with dummy head Audio CD for subjective test and signal for characterization of car inside Reproduce the Audio track, recorded in several car, in Virtual system Use for audio comparison an automatic software developed in VB University of Parma

Virtual listening system Virtual system: Double stereo dipole Two central channel for voice and monophonic signal Two surround channel for reproduction of high uncorrelated signal and aimed to recreate lateral contribution from loudspeaker in car PC & Audio Card (Digital Out) DSP SHARC PC & Audio Card (8 In, 10 Out) Power amplifier Power amplifier Power amplifier Power amplifier Front stereo dipole Rear stereo dipole 2 lateral loudspeakers 2 bottom loudspeakers Subwoofer

Virtual listening system Virtual system Plant: Stereo Dipole Front Stereo Dipole Rear Surround loudspeaker Central Channel

Algorithm for sound field correction University of Parma

Algorithm for sound field correction Existing algorithms: Time delay alignment Stereo dipole for new configuration system (dedicate loudspeaker + central channel) Psychoacoustic curve correction (Aqt Filter) Algorithms under test Stereo dipole for standard system configuration Resonance and tail correction system (Aqt Filter) In the future >> Surround system: 5+1 Platform: DSP board Technique: FIR Filtering University of Parma

Algorithm for sound field correction Time delay alignment: Compensate the time difference existing between the time arrival of the direct sound of the two hearing channel Create a virtual symmetric system Enhance spatial sensation and create a wide scene in the driver position Stereo dipole for new configuration system: Need a couple of loudspeaker for each seat Enhance spatial sensation and create a wide scene in all the listening position Perform Cross-Talk and reduce resonance and reflection effects on the hearing University of Parma

Algorithm for sound field correction Psychoacoustic curve correction: Invert dynamic curve response of car cockpit really perceived by hearing system Perform more pleasant filter than standard inversion technique A tool is already developed to perform this: AQT Tool University of Parma

Digital system simulation University of Parma

Digital system simulation Overview: its a difficult task compare a lot of algorithm and set of coefficients at the same time on DSP board Solution >> Simulation System on PC Goal: Simulate different digital system for correction of the response inside the car: Stereo Dipole Filtering, IIR, FIR,AQT Filter, 5+1 surround system Compare different configuration staying in listening position Features: Let us to compare all the algorithms in real time and perform a fast switching between different configuration (Ex: 5+1 vs Cross Talk) Let us to compare in a fast way several set of coefficients of FIR, IIR, AQT filter and to choose the set that retrieves the best performance and pleasure PERMIT ON THE ROAD TEST!!!

Car inside digital system simulation Simulation system: A Notebook Existing Software: digital block performing several algorithm Accept extern block programmed in VST standard We already have all the block that permit the simulation of the entire set of developed algorithm We have the know-how to perform new VST plug-in for new algorithm A multichannel (10 or more) Sound Card with PCIMCA interface as Echo Layla >> WE NEED IT!!! Amplifiers to drive all the loudspeaker

Car inside digital system simulation Simulation Block Diagram: Notebook PCIMCA Multichannel Audio card Multichannel Power Amplifier Standard system Stereo dipole system 5+1 surround system

Reliable measure technique University of Parma

Reliable measure technique for IR Goal: Introduce the Impulse Response as standard measure for characterization of the car inside Introduce the use of Cool-Edit and Aurora for IR measure Introduce AQT Tool as advanced analysis system Perform reliable and repeatable measures of response inside the car testing several procedures of average of binaural recording THE ACTUAL APPROACH: Binaural recording of IR with rotating dummy head by step of 15 degrees 0o0o -15 o +15 o