The eigenspectra of Indian musical drums

In a family of drums used in the Indian subcontinent, the circular drum head is made of material of non-uniform density. Remarkably, and in contrast to a circular membrane of uniform density, the low eigenmodes of the non-uniform membrane are harmonic. In this work we model the drum head by a non-uniform membrane whose density varies smoothly between two prescribed values. Using a Fourier-Chebyshev spectral collocation method we obtain the eigenmodes and eigenvalues of the drum head. For a suitable choice of parameters, which we find by optimising a cost function, the eigenspectra obtained from our model are in excellent agreement with experimental values. Our model and the numerical method should find application in numerical sound synthesis

Synchronization of Sound Sources

Sound generation and -interaction is highly complex, nonlinear and self-organized. Already 150 years ago Lord Rayleigh raised the following problem: Two nearby organ pipes of different fundamental frequencies sound together almost inaudibly with identical pitch. This effect is now understood qualitatively by modern synchronization theory (M. Abel et al., J. Acoust. Soc. Am., 119(4), 2006). For a detailed, quantitative investigation, we substituted one pipe by an electric speaker. We observe that even minute driving signals force the pipe to synchronization, thus yielding three decades of synchronization -- the largest range ever measured to our knowledge. Furthermore, a mutual silencing of the pipe is found, which can be explained by self-organized oscillations, of use for novel methods of noise abatement. Finally, we develop a specific nonlinear reconstruction method which yields a perfect quantitative match of experiment and theory.Comment: 5 pages, 4 figure

Animal-Computer Interaction (ACI): a manifesto

Although we have involved animals in machine and computer interactions for a long time, their perspective has seldom driven the design of interactive technology meant for them and animal-computer interaction is yet to enter mainstream user-computer interaction research. This lack of animal perspective can have negative effects on animal users and on the purposes for which animal technology is developed. Not only could an Animal-Computer Interaction (ACI) agenda mitigate those effects, it could also yield multiple benefits, by enhancing our inter-species relationships with the animals we live or work with, leading to further insights into animal cognition, rendering conservation efforts more effective, improving the economical and ethical sustainability of food production, expanding the horizon of user-computer interaction research altogether and benefiting different groups of human users too. Advances in both our understanding of animal cognition and computing technology make the development of ACI as a discipline both possible and timely, while pressing environmental, economic and cultural changes make it desirable. But what exactly is ACI about and how could we develop such a discipline? This Manifesto describes the scientific aims, methodological approach and ethical principles of ACI and proposes a research agenda for its systematic development