Researches and Applications for Automotive Field

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Researches and Applications for Automotive Field

Andrea Azzali, Eraldo Carpanoni, Angelo Farina

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Topics

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

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Innovative dynamic analysis technique

AQT Tool

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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

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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

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Objective evaluation system

Evaluation Test

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Objective evaluation system

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)

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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

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Objective evaluation system

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)

• ……..

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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

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Virtual listening system

Listening

room

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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

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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

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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 21161

PC

&

Audio Card

(8 In, 10 Out)

Power amplifier

Front stereo dipole

Rear stereo dipole

2 lateral

loudspeakers

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Virtual listening system

Virtual system Plant:

Stereo Dipole

Front

Stereo

Surround loudspeake

r Central

Channel

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Algorithm for sound field

correction

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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:

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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

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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

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Digital system simulation

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Digital system simulation

Overview:

⇨ it’s 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

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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!!!

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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

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Reliable measure technique

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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 ^-15

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