Genotypic variability enhances the reproducibility of an ecological study

Many scientific disciplines are currently experiencing a “reproducibility crisis” because numerous scientific findings cannot be repeated consistently. A novel but controversial hypothesis postulates that stringent levels of environmental and biotic standardization in experimental studies reduces reproducibility by amplifying impacts of lab-specific environmental factors not accounted for in study designs. A corollary to this hypothesis is that a deliberate introduction of controlled systematic variability (CSV) in experimental designs may lead to increased reproducibility. We tested this hypothesis using a multi-laboratory microcosm study in which the same ecological experiment was repeated in 14 laboratories across Europe. Each laboratory introduced environmental and genotypic CSV within and among replicated microcosms established in either growth chambers (with stringent control of environmental conditions) or glasshouses (with more variable environmental conditions). The introduction of genotypic CSV led to lower among-laboratory variability in growth chambers, indicating increased reproducibility, but had no significant effect in glasshouses where reproducibility was generally lower. Environmental CSV had little effect on reproducibility. Although there are multiple causes for the “reproducibility crisis”, deliberately including genetic variation may be a simple solution for increasing the reproducibility of ecological studies performed in controlled environments

Visually adaptive virtual sound imaging using loudspeakers

Advances in computer technology and low cost cameras open up new possibilities for three dimensional (3D) sound reproduction. The problem is to update the audio signal processing scheme for a moving listener, so that the listener perceives only the intended virtual sound image. The performance of the audio signal processing scheme is limited by the condition number of the associated inversion problem. The condition number as a function of frequency for different listener positions and rotation is examined using an analytical model. The resulting size of the "operational area" with listener head tracking is illustrated for different geometries of loudspeaker configurations together with related cross-over design techniques. An objective evaluation of cross-talk cancellation effectiveness is presented for different filter lengths and for asymmetric and symmetric listener positions. The benefit of using an adaptive system compared to a static system is also illustrated. The measurement of arguably the most comprehensive KEMAR database of head related transfer functions yet available is presented. A complete database of head related transfer functions measured without the pinna is also presented. This was performed to provide a starting point for future modelling of pinna responses. The update of the audio signal processing scheme is initiated by a visual tracking system that performs head tracking without the need for the listener to wear any sensors. The solution to the problem of updating the filters without any audible change is solved by using either a very fine mesh for the inverse filters or by using commutation techniques.The filter update techniques are evaluated with subjective experiments and have proven to be effective both in an anechoic chamber and in a listening room, which supports the implementation of virtual sound imaging systems under realistic conditions. The design and implementation of a visually adaptive virtual sound imaging system is carried out. The system is evaluated with respect to filter update rates and cross-talk cancellation effectiveness