In this article we present an approach that uses sound to communicate geometrical data related to a virtual object. This has been developed in the framework of a multimodal interface for product design. The interface allows a designer to evaluate the quality of a 3-D shape using touch, vision, and sound. Two important considerations addressed in this article are the nature of the data that is sonified and the haptic interaction between the user and the interface, which in fact triggers the sound and influences its characteristics. Based on these considerations, we present a number of sonification strategies that are designed to map the geometrical data of interest into sound. The fundamental frequency of various sounds was used to convey the curve shape or the curvature to the listeners. Two evaluation experiments are described, one involves partipants with a varied background, the other involved the intended users, i.e. participants with a background in industrial design. The results show that independent of the sonification method used and independent of whether the curve shape or the curvature were sonified, the sonification was quite successful. In the first experiment participants had a success rate of about 80% in a multiple choice task, in the second experiment it took the participants on average less than 20 seconds to find the maximum, minimum or inflection points of the curvature of a test curve.

Tangible user interfaces have been promoted and discussed in the Ubicomp and HCI communities for 15 years. In TUIs physical objects are used for the control and representation of digital information, similarly to how icons are used in graphical user interfaces for the same purpose. Most reported TUI systems have the nature of research prototypes, available in laboratories or museums. This paper reports an attempt to understand the impact of TUIs in users' everyday environments through 2 low-cost simple set-up tangible interfaces for music that can be freely downloaded from a website. The systems are based on computer vision, printed paper and audio output. A few hundreds of users downloaded them and played with them. We logged users interaction with the interfaces and analysed content posted by them on our own and other web sites to observe and evaluate how they relate to such novel systems, taking measures to protect their privacy. Both the interaction logs and the users' comments indicate that the tangible interfaces were accepted as normal: they were perceived just as interfaces to make music rather than esoteric systems. Its time to bring Ubicomp technology to the masses!

The digital waveguide mesh can be used to simulate the propagation of sound waves in an acoustic system. The accurate simulation of the acoustic characteristics of boundaries within such a system is an important part of the model. One significant property of an acoustic boundary is its diffusivity. Previous approaches to simulating diffuse boundaries in a digital waveguide mesh are effective but exhibit limitations and have not been analyzed in detail. An improved technique is presented here that simulates diffusion at boundaries and offers a high degree of control and consistency. This technique works by rotating wavefronts as they pass through a special diffusing layer adjacent to the boundary. The waves are rotated randomly according to a chosen probability function and the model is lossless. This diffusion model is analyzed in detail, and its diffusivity is quantified in the form of frequency dependent diffusion coefficients. The approach used to measuring boundary diffusion is described here in detail for the 2-D digital waveguide mesh and can readily be extended for the 3-D case.