Frank Wefers

Virtual reality for architectural acoustics

Over the last decades, powerful prediction models have been developed in architectural acoustics, which are used for the calculation of sound propagation in indoor and/or outdoor scenarios. Sound insulation is predicted rather precisely by using direct and flanking transmission models of sound and vibration propagation. These prediction tools are already in use in architectural design and consulting. For the extension towards virtual reality (VR) systems, it is required to accelerate the prediction and simulation tools significantly and to allow an adaptive and interactive data processing during the simulation and 3D audio stimulus presentation. This article gives an overview on the current state-of-the-art of acoustic VR and discusses all relevant components in terms of accuracy, implementation and computational effort. With the progress in processing power, it is already possible to apply such VR concepts for architectural acoustics and to start perceptual studies in integrated architectural design processes.

Interdisciplinary Auralization of Take-off and Landing Procedures for Subjective Assessment in Virtual Reality Environments

The issue of aircraft noise experienced by residents in the airport’s neighborhoods is one of subjective annoyance and a presentation of noise intensity in decibels alone might not be sufficient to give a clear understanding of noise abatement measures being carried out or the effect for instance of constructing a new runway at an airport. Although noise contours can be a great way of a quick assessment of noise impact over larger areas, noise quantified in numbers can prove lacking in capturing the actual annoyance caused by the noise to the residents. For this reason, a method providing a more subjective assessment of aircraft noise impact is required and auralization of complete aircraft movements could be one such way of better capturing the annoyance due to noise caused by aircraft. The Virtual Air Traffic System Simulation (VATSS) interdisciplinary project of RWTH Aachen University has the aim of presenting the effect of complete aircraft movements via visualization and auralization of aircraft noise in 3-D Virtual Reality environments for the subjective assessment of aircraft noise. This paper focusses on the interdisciplinary collaboration of the Institute of Aerospace Systems and the Institute of Technical Acoustics of RWTH Aachen to produce a capability of auralizing complete time-dependent take-off and landing procedures up to an altitude of 3000 meters. The noise produced by a conventional aircraft with a turbofan engine is modeled and the ILR’s capability to model aircraft noise for complete 4-D take-off and landing procedures is shown along with the technique to auralize complete standard procedures as well as noise abatement procedures with time-varying settings. Both broadband and tonal noise components for dominant sources are auralized for the movements.

Virtual air traffic system simulation — Aiding the communication of air traffic effects

A key aspect of air traffic infrastructure projects is the communication between stakeholders during the approval process regarding their environmental impact. Yet, established means of communication have been found to be rather incomprehensible. In this paper we present an application that addresses these communication issues by enabling the exploration of airplane noise emissions in the vicinity of airports in a virtual environment (VE). The VE is composed of a model of the airport area and flight movement data. We combine a real-time 3D auralization approach with visualization techniques to allow for an intuitive access to noise emissions. Specifically designed interaction techniques help users to easily explore and compare air traffic scenarios.

Flexible data structures for dynamic virtual auditory scenes

Virtual environments and their contents are dynamically changing, but also need to respond to the user immediately. While managing a dynamic scene is a common and well-understood problem for visual rendering, additional challenges exist for the high-quality audio rendering of such scenes. Audio rendering differs in a key aspect: Sound waves propagate substantially slower than light. For the acoustics in scenes of large dimensions, it is not sufficient to regard just the state at the current time. The sound propagation times become so significant (perceptible) that the past of the objects matter, making a time history of the scene necessary. Particularly the conjunction of multithreading and low-latency audio processing makes the description of the virtual acoustic scene a problem on its own. This paper presents a novel solution to this acoustic-related problem. We discuss the challenges of realizing a real-time auralization on modern (non-real-time) operating systems and state the main requirements of the data structure. A hierarchical state-based data structure with time history is presented, which not only fulfills the requirements for outdoor auralizations but also has key advantages for indoor simulations—such as room acoustics. A key feature is the integral support of atomic scene modifications, allowing several modifications to be performed at the same time. The presented concept is very modular and beneficial for a wide range of applications.

Virtual Room Acoustics

The technology for creating an Acoustic Virtual Reality for wide variety of applications has been developed in the last decade. An important requirement of Virtual Reality is the multimodal approach which includes vision, sound, tactile and haptic stimuli. The process of creating a physical stimulus based on computer data is called “rendering”. The development of rendering and reproduction of acoustic stimuli in VR is now at a stage where integration of spatial room sound is feasible by using PCs. This applies to multi-channel binaural synthesis as well as to full room-acoustic simulation algorithms. In this chapter the basic concepts of real-time room acoustic simulation, early reflections’ and spatial reverberation rendering, binaural reproduction technology and dynamic realtime audio signal processing are presented.