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Jens Blauert, D-Bochum

From Binaural Technology to Virtual Reality

Prominent Features of Binaural Hearing

- LocalizationFormation of positions of the auditory events(azimuth, elevation, distance, spatial extent),auditory room impression, immersion

- Suppression ofthe directional information coming from reflections(Precedence Effect, localization dominance, fusion), reverberation, coloration and noise

- Identification & segregation ofauditory streams,e.g., concurrent talkers (Cocktail-Party Effect)

Prominent Features of Binaural Hearing

- Introduction- Authentic Recording, Transmission & Reproduction- Processing & Analysis of Binaural Signals- Binaural Display & Room Simulation- Interactivity, Virtual Reality- Conclusions

From Binaural Technologyto Virtual Reality

From Binaural Technology to Virtual Reality

AuthenticReproduction

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Binaural Technology (I)Dummy-Head Designsof Different Complexity

HMS I

HMS III

KU 80 KU 81

1/8 th scale

Measuring Head-RelatedTransfer Functions (HRTFs)

- little electret microphones,inserted into the ear canals

- measuring signals are, e.g.:noise, impuls trains or sinusoids

- anechoic chamber

laserpositioncontrol

mikecable

A Set of Binaural Impulse Responses

Localization Errors with Non-optimumHRTFs

Perc

eive

dD

irect

ion

Representative HRTFs

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Parametric Modelling of the External Ear Binaural Technology (I)

Binaural Technology (IIa)

(c)

Binaural Technology (IIa)

binaural-activity display

Architecture for a Model of Binaural Hearing

Structure of theModel ofBinaural Hearing

binaural-activity map

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left < lateral deviation > right

Output of the Binaural Model: Impuls Response of a Concert Hall

critical band around 700 Hz

runn

ing

time

left < lateral deviation > right left < lateral deviation > right

Binaural Exitation Patterns of Two Different Concert Halls

Gasteig, G-Munich Musikvereinsaal, Vienna

critical band about 700 Hz, 250-ms shot

Blauert 1988

Potential Applications for Binaural AlgorithmsSuitable for Short-Term Implementation

Binaural Technology at its Best- provided that binaural signals are used

Binaural Technology (IIa)

Binaural Technology (IIb)

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Binaural Synthesis of Sound Fields in Enclosures Ray Tracing

Mirror Imaging

Binaural-Room-SimulationSystem

coarse resolution48 planes

finest resolution238 planes

medium resolution126 planes

Checking forPerceptual Authenticity inBinaural Room Simulation

Room-Acoustics&Sound-SystemsPlanning

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Interactive Systems Virtual Reality

Differences of Measured and Simulated Impulse Responses

Measuring a Pre-Set Real Environment Binaural Room Scanning (BRS)The Complete System

Head-RelatedPlay Back

Binaural Technology (IIc)

interactivity

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Experimental ParadigmPartners: Aalborg University, Denmark; Bochum University, Head Acoustics, Germany;

Pisa University, Sciencia Machinale, Italy.

The SCATIS Lab, an experimental audio/tactile interactive virtual environment

The Scenario of the SCATIS Lab

Architecturof theSCATIS-LabVirtual-RealityGenerator

Schematic of the SCATIS Lab

The SCATIS Glove SCATIS-Hardware Overviewacquired 1995

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requirements:

“smoothness”frame rate > 16/s(depending on speed ofmovements involved)

“responsiveness”delay < 60 ms

actually achievable with PCs of 2004:40 sound sources, moving at moderate speed.

frame rate 20/sdelay 20 ms

The Problem of “Realtimeability”Lehnert, 1994

List of Events Relevant to the Sound-Field Model

arrival time spectral modification HRTFs

Filter Structure for the Convolution of „Dry“ SignalsDoppler Shifts and Visibility Checkfor Moving Sound Sources

Problems in a TeleconferenceSetting

Perception of One‘s Own VoicePörschmann (2001)

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Major computational demands arise from the sound-field model whichgenerates realistic room responses, and from the aurilization enginewhich spatializes primary and reflective sounds. With today‘s PCs, up to about 200 sound sources incl. mirror sources can be handled in real time. For distributed sound sources and reverberation dedicated, computationallyeffective algorithms are usually employed.

Virtual Auditory Environments – Auditory DisplaysSome Final Statements:

Vision of a Multimodal Tele-Conferencing System

control rooms !

Generic Application Areas of Binaural Technology− a Summary −

Thank you!

jens.blauert@rub.dehttp://www.ruhr-uni-bochum.de/ika

Copyright note:

This material is not in the public domain.The author(s) claim(s) all applicable rights.However, permission to copy it is granted under the condition that proper reference is given to the author(s).

Corresponding author:

------------------------------------------------------------Jens Blauert, Professor emeritus of Acoustics

Institute of Communication AcousticsRuhr-Universitaet BochumD-44780 Bochum, Germany

Tel.: +49 234 322 2496 (direct: 3480)Fax: +49 234 321 4165e-mail: jens.blauert@rub.dehttp://www.rub.de/ika

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