Progress in Auditory Perception Research Laboratories—Multimodal Measurement Laboratory of Dresden University of Technology

This article presents the general ideas and implementation details of the MultiModal Measurement Laboratory (MMM Lab) of Dresden University of Technology. This lab combines VR equipment for multiple modalities (auditory, tactile, vestibular, visual) and is capable of presenting high-performance, interactive simulations. The goals are to discuss the progress in auditory perception research laboratories in recent years and the technical parameters, which should be considered for the implementation of reproduction systems for different modalities. 1. AUDITORY PERCEPTION RESEARCH Psychoacoustics aims to model the perception of sound. It concerns itself with the relationship between physical sound events and their perception. The data, which is required for investigating and modeling the rules of perception, is gathered through listening experiments. The presentation of an identical stimulus for all subjects in a well-defined acoustical environment should be guaranteed for such kind of experiments. Therefore most of the classical psychoacoustic investigations, such as threshold measurements, auditory masking experiments, etc., were and are still conducted in soundinsulating audiometry booths. However we perceive our world in a multimodal way. In our daily life we permanently obtain information about products through all our senses during product use. In many situations, such as driving a car, drilling a hole, playing a guitar etc., we are exposed to sound, vibration and visual information simultaneously. Consequently, the cross-modal information has a substantial influence on the perception of the user [1]. Hence a perceived sound is not just a sensation, but also carrier of information from and about the environment – sound has a meaning. For example, in product sound 8305 Altinsoy et al. AUDITORY & MULTIMODAL RESEARCH AES 129th Convention, San Francisco, CA, USA, 2010 November 4–7 Page 2 of 8 quality evaluation, the context, the ambience and the interaction play a very important role. Therefore the research in the fields of product sound quality, communication acoustics and semioacoustics requires multimodal interactive simulators which can emulate our daily situations plausibly. Virtual reality provides the user real-time multi-sensory interaction with the computer-generated environment. Virtual reality generators have proved to be potent tools for research and development. They allow for flexible and economic presentation of complex experimental scenarios which can be modified without any physical effort [2]. 2. MOTIVATION AND REQUIREMENTS Taking into account the above-mentioned aspects, Chair of Communication Acoustics at Dresden University of Technology decided to build a new Multimodal Measurement Laboratory. The main questions addressed in MMM lab are: • How does a human listener manage to select certain characteristic features from the auditory event and take them as information carrying units, i.e. as sign carriers? • How do human listeners associate meaning to acoustic-auditory events? • How does the brain weigh the inputs it receives from the different senses to produce a final percept? In other words, what are the relative contributions of the different sensory modalities to the multimodal percept? • Can a perception of an event in one sensory modality change due to the presence of a stimulus in another sensory modality? • How do we perceive product quality globally? How do we judge auditory and tactile product quality separately? In order to investigate these questions and to simulate different daily-life situations such as driving a car, experiencing a concert or flying with an airplane, we decided to present acoustic, motion, vibration, forcefeedback and visual stimuli to the subjects. Currently developed reproduction technologies were selected for these different modalities. Acoustic stimulation was realized by a wave field synthesis system. The motion and vibration feedback are generated by a six degree of freedom hydraulic motion platform. The visual information is displayed by a Full HD video projector. In principle, wave-field synthesis (WFS) attempts to simulate the spatial sound-field and it is based on freefield wave propagation. Therefore the reflections of the reproduction room should be suppressed. Theoretically the best reproduction room for the WFS is an anechoic chamber. However anechoic chamber conditions are unusual for most of our test participants (particularly for inexperts) and cause on them estrangement with the experiment which is undesirable for the contextualization. Therefore we decided that the reproduction room should be built according to listening room recommendations rather than anechoic chamber conditions. One of the important challenges by building a multimodal measurement laboratory is that the reproduction systems for other modalities such as motion, video etc. should be very quiet and don’t disturb the acoustic reproduction and environment. 3. LABORATORY COMPLEX MMM laboratory complex consists of four rooms to conduct perception experiments (Figure 1): • an instruction room to instruct the test persons • a control room for the experimenter • measurement laboratory – reproduction room