Two experiments have been conducted to investigate the perceptual effect of band-limited interchannel decorrelation between vertically oriented loudspeakers. The perceived vertical image spread (VIS) and tonal quality (TQ) of phantom auditory images have been subjectively assessed in multiple comparison trials. The aim of the article was to find a lower decorrelation boundary that provides a significant increase of VIS, whilst maintaining TQ close to that of the original source. For test stimuli, decorrelation was applied to natural sound sources and pink noise in groups of octave-bands, where the lowest band was varied between 63 Hz and 8 kHz and the upper band was fixed at 16 kHz, resulting in eight decorrelated conditions for each source. Unprocessed octave-bands below the lower boundary were reproduced simultaneously through the lower main-layer loudspeaker only, and a monophonic main-layer only condition was also included in the comparison alongside the decorrelated stimuli. Results reveal that vertical decorrelation of the 500 Hz octave-band and above tends to significantly increase VIS, similar to that of broadband decorrelation, with little impact on TQ. In some cases, decorrelation of higher octave-bands and above can also produce similar increases of VIS with less impact on TQ, however, this is shown to be largely source-dependent. These results suggest that vertical decorrelation of lower frequencies has little perceptual benefit, and band-limiting vertical decorrelation to higher frequencies is likely to reduce low frequency phase cancellation. Applications of such an approach include 2D-to-3D upmixing and binaural audio rendering, with additional implications for 3D audio recording.

MOTIVATION: With the advancement of high-throughput techniques, large-scale profiling of biological systems with multiple experimental perturbations is becoming more prevalent. Pathway analysis incorporates prior biological knowledge to analyze genes/proteins in groups in a biological context. However, the hypotheses under investigation are often confined to a 1D space (i.e. up, down, either or mixed regulation). Here, we develop direction pathway analysis (DPA), which can be applied to test hypothesis in a high-dimensional space for identifying pathways that display distinct responses across multiple perturbations. RESULTS: Our DPA approach allows for the identification of pathways that display distinct responses across multiple perturbations. To demonstrate the utility and effectiveness, we evaluated DPA under various simulated scenarios and applied it to study insulin action in adipocytes. A major action of insulin in adipocytes is to regulate the movement of proteins from the interior to the cell surface membrane. Quantitative mass spectrometry-based proteomics was used to study this process on a large-scale. The combined dataset comprises four separate treatments. By applying DPA, we identified that several insulin responsive pathways in the plasma membrane trafficking are only partially dependent on the insulin-regulated kinase Akt. We subsequently validated our findings through targeted analysis of key proteins from these pathways using immunoblotting and live cell microscopy. Our results demonstrate that DPA can be applied to dissect pathway networks testing diverse hypotheses and integrating multiple experimental perturbations. AVAILABILITY AND IMPLEMENTATION: The R package 'directPA' is distributed from CRAN under GNU General Public License (GPL)-3 and can be downloaded from: http://cran.r-project.org/web/packages/directPA/index.html CONTACT: [email protected] SUPPLEMENTARY INFORMATION: Supplementary data are available at Bioinformatics online.