Efficient physics-based room-acoustics modeling and auralization

The goal of this research is to develop efficient algorithms for physics-based room acoustics modeling and real-time auralization. Given the room geometry and wall materials, in addition to listener and sound source positions and other properties, the auralization system aims at reproducing the sound as would be heard by the listener in a corresponding physical setup. A secondary goal is to predict the room acoustics parameters reliably. The thesis presents a new algorithm for room acoustics modeling. The acoustic radiance transfer method is an element-based algorithm which models the energy transfer in the room like the acoustic radiosity technique, but is capable of modeling arbitrary local reflections defined as bidirectional reflectance distribution functions. Implementing real-time auralization requires efficient room acoustics modeling. This thesis presents three approaches for improving the speed of the modeling process. First, the room geometry can be reduced. For this purpose an algorithm, based on volumetric decomposition and reconstructions of the surface, is described. The algorithm is capable of simplifying the topology of the model and it is shown that the acoustical properties of the room are sufficiently well preserved with even 80 % reduction rates in typical room models. Second, some of the data required for room acoustics modeling can be precomputed. It is shown that in the beam tracing algorithm a visibility structure called "beam tree" can be precomputed efficiently, allowing even moving sound sources in simple cases. In the acoustic radiance transfer method, effects of the room geometry can be precomputed. Third, the run-time computation can be optimized. The thesis describes two optimization techniques for the beam tracing algorithm which are shown to speed up the process by two orders of magnitude. On the other hand, performing the precomputation for the acoustic radiance transfer method in the frequency domain allows a very efficient implementation of the final phase of the modeling on the graphics processing unit. An interactive auralization system, based on this technique is presented

Geometriareduktion hyödyntäminen huoneakustiikan mallinnuksessa

Tämä diplomityö esittelee menetelmän monimutkaisten huonemallien geometrian pelkistämiseksi, jotta niiden akustinen mallintaminen olisi mahdollista reaaliajassa. On näytetty, että geometrian pelkistäminen voi lyhentää mallinnusaikaa huomattavasti. Tätä päätelmää tukevat kokeelliset tulokset. Aiemmin kirjallisuudessa esitettyjä menetelmiä geometristen mallien yksinkertaistamiseksi esitellään laajalti. Katsaus ryhmittelee ne harvennus- ja pinnan uudelleenrakennusmenetelmiin. Harvennusmenetelmät on edelleen jaettu pisteenpoisto-, pisteidenyhdistämis-, reunanromautus-, ja kolmionpoistoalgoritmeihin. Pinnan uudelleenrakennusmenetelmät sisältävät uudelleenverkottamis- ja tilavuuspohjaiset lähestymistavat. Tämän diplomityön tärkein osuus on menetelmä geometristen mallien pelkistämiseksi akustista mallintamista varten. Se koostuu kahdesta askeleesta: topologian yksinkertaistamisesta ja geometrian pelkistämisestä. Topologian pelkistämiseen ehdotetaan kahta lähestymistapaa, josta toinen pohjautuu säännölliseen tiheysruudukkoon ja toinen octree-rakenteeseen. Myös geometrian pelkistämiseen sovelletaan kahta algoritmia, joista molemmat yrittävät sulauttaa pieniä samassa tasossa olevia kolmioita suuriksi monikulmioiksi. Pelkistysmenetelmän tuloksia arvioidaan käyttäen akustisia tunnuslukuja. Myös menetelmän suorituskykyä on analysoitu. Kokeet osoittavat, että algoritmi säilyttää tilaominaisuudet, joita on mitattu jälkikaiunta-ajalla, suhteellisen hyvin. Algoritmi voi tuottaa karkeimman tason malleja reaaliajassa, mutta tarkemmat mallit vaativat huomattavasti pitempiä laskenta-aikoja

Concert hall geometry optimization with parametric modeling tools and wave-based acoustic simulations

VK: Lokki, SaviojaPeer reviewe

A distributed real-time virtual acoustic rendering system for dynamic geometries

A novel room acoustic simulation system capable of producing interactive sound environments in dynamic and complex 3D geometries is introduced. The system is distributed to several modules that share the same 3D geometry. All changes made by one module are updated in all the other modules in real time. The auralization tools of the system include a geometry reduction tool, a beam tracing algorithm, and a sound rendering application. The geometry reduction simplifies 3D models for beam tracing module that forwards direct sound and early reflection paths for sound rendering. The sound rendering application contains a automatic estimation of late reverberation parameters, based on early reflections

Framework for Real-Time Auralization in Architectural Acoustics

cote interne IRCAM: Noisternig08aNone / NoneNational audienceAuralization is the process of making audible the acoustics of complex virtual architectural spaces in a realistic and accurate manner. This paper presents a novel real-time auralization software environment comprising a room acoustic modeler, a spatial renderer for auralization, and a visualization and scene graph unit for interactivity. The computation of early reflection paths within the geometric model is based on an efficient beam tracing algorithm capable of real-time detection of specular reflection paths in a static geometry with one or several moving listener(s). For “simple" rooms, the real-time performance is maintained even with dynamic geometries and sources. Results of the room acoustic model consisting of visible reflection paths and their accumulated material attenuation are sent to the audio renderer. From this geometrical and acoustical data, listener position-relative 3D room impulse responses are generated using a hierarchical-order Ambisonics approach. Finally, the spatialized audio output is presented to the listener via multiple loudspeakers or binaurally rendered over headphones. As higher order reflections are more diffuse in nature, they are encoded using lower Ambisonic orders, thereby reducing computational load. The environment combines high quality audio with visual rendering realized using the open source platforms Pure Data and VirChor respectively. This open source auralization framework provides direct audio-visual interaction in real-time and is suitable for VR environments

Geometry reduction in room acoustics modeling

This thesis represents a method for reducing the geometry of complex room models to make it possible to model their acoustics in real-time. It is shown that reducing geometry can vastly decrease the modeling time. This conclusion is supported by the experimental results. The previous work on geometric model simplification is surveyed extensively. The re-duction algorithms are grouped into decimation algorithms and surface reconstruction algorithms. The decimation algorithms are categorized into vertex removal, vertex clustering, edge collapsing, and triangle removal algorithms. The surface reconstruction algorithms include re-meshing and volumetric approaches. The main contribution of this thesis is a method for reducing geometric models for acoustics modeling. It consists of two steps: topology simplification and geometry reduction. Two approaches are suggested for the topology simplification, one based on a regular density grid and another based on an octree. There are also two algorithms for the geometry reduction both of which are trying to merge small coplanar triangles into large polygons. The results of the reduction method are evaluated using the acoustical parameters. Also the performance of the reduction algorithm is analyzed. The experiments show that the algorithm preserves spatial properties, measured by the reverberation time, relatively well. The algorithm can produce coarsest level approximations in real-time, but more accurate approximations require significantly longer times for computation

Acoustic visualizations using surface mapping

VK: Lokki, SaviojaPeer reviewe