Visualizing sound emission of elephant vocalizations: evidence for two rumble production types

Recent comparative data reveal that formant frequencies are cues to body size in animals, due to a close relationship between formant frequency spacing, vocal tract length and overall body size. Accordingly, intriguing morphological adaptations to elongate the vocal tract in order to lower formants occur in several species, with the size exaggeration hypothesis being proposed to justify most of these observations. While the elephant trunk is strongly implicated to account for the low formants of elephant rumbles, it is unknown whether elephants emit these vocalizations exclusively through the trunk, or whether the mouth is also involved in rumble production. In this study we used a sound visualization method (an acoustic camera) to record rumbles of five captive African elephants during spatial separation and subsequent bonding situations. Our results showed that the female elephants in our analysis produced two distinct types of rumble vocalizations based on vocal path differences: a nasally- and an orally-emitted rumble. Interestingly, nasal rumbles predominated during contact calling, whereas oral rumbles were mainly produced in bonding situations. In addition, nasal and oral rumbles varied considerably in their acoustic structure. In particular, the values of the first two formants reflected the estimated lengths of the vocal paths, corresponding to a vocal tract length of around 2 meters for nasal, and around 0.7 meters for oral rumbles. These results suggest that African elephants may be switching vocal paths to actively vary vocal tract length (with considerable variation in formants) according to context, and call for further research investigating the function of formant modulation in elephant vocalizations. Furthermore, by confirming the use of the elephant trunk in long distance rumble production, our findings provide an explanation for the extremely low formants in these calls, and may also indicate that formant lowering functions to increase call propagation distances in this species'

Retrieval of visual composition in film

The spatial arrangement of visual elements of an image, i.e. the visual composition, is a research subject in the domain of visual arts which include painting, film, etc. Film experts face the problem of retrieval of visual compositions in film on a daily basis. Although, visual composition is a crucial element to consider in content-based video retrieval, little scientific effort has been invested into this problem so far. Actually, it is unclear if content-based retrieval of visual compositions is feasible. We present a user study conducted to investigate the feasibility of content-based retrieval of visual compositions as they are understood by film experts. For that reason, we create a data set derived from real world material and let the film experts evaluate the retrieval performance. The user study investigates the applicability of state-of-the-art visual features and shows differences in evaluations by film experts (test group) and computer scientists (reference group)

Combined Discrete-event Simulation and Ant Colony Optimisation Approach for Selecting Optimal Screening Policies for Diabetic Retinopathy

Screening for diabetic retinopathy, Discrete event simulation, Ant colony optimisation, Cost-effectiveness analysis, Decision-support system,