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Researches and Applications for
Automotive Field
Andrea Azzali, Eraldo Carpanoni, Angelo Farina
University
of Parma
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
University of Parma
Innovative dynamic analysis technique
AQT Tool
University of Parma
Innovative dynamic analysis technique
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
University of Parma
AQT Analysis system
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
University of Parma
Objective evaluation system
Evaluation Test
University of Parma
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)
University of Parma
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
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)
……..
University of Parma
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
Listening room
University of Parma
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 doesn’t 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
DSP SHARC
21161
PC
&
Audio Card
PC
&
Audio Card
(Digital Out)
DSP SHARC
21161
(8 In, 10 Out)
Power
amplifier
Front
stereo dipole
Power
amplifier
Rear
stereo dipole
Power
amplifier
2 lateral
loudspeakers
Power
amplifier
2 bottom
loudspeakers
Subwoofer
Virtual listening system
Virtual system Plant:
Stereo
Dipole
Front
Central
Channel
Surround
loudspeaker
Stereo
Dipole
Rear
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:
⇨ 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 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:
Standard
system
Notebook
PCIMCA
Multichannel
Audio card
Multichannel
Power Amplifier
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
-15o
0o
+15o