Real-time sound synthesis on a multi-processor platform

Real-time sound synthesis means that the calculation and output of each sound sample for a channel of audio information must be completed within a sample period. At a broadcasting standard, a sampling rate of 32,000 Hz, the maximum period available is 31.25 μsec. Such requirements demand a large amount of data processing power. An effective solution for this problem is a multi-processor platform; a parallel and distributed processing system. The suitability of the MIDI [Music Instrument Digital Interface] standard, published in 1983, as a controller for real-time applications is examined. Many musicians have expressed doubts on the decade old standard's ability for real-time performance. These have been investigated by measuring timing in various musical gestures, and by comparing these with the subjective characteristics of human perception. An implementation and its optimisation of real-time additive synthesis programs on a multi-transputer network are described. A prototype 81-polyphonic-note- organ configuration was implemented. By devising and deploying monitoring processes, the network's performance was measured and enhanced, leading to an efficient usage; the 88-note configuration. Since 88 simultaneous notes are rarely necessary in most performances, a scheduling program for dynamic note allocation was then introduced to achieve further efficiency gains. Considering calculation redundancies still further, a multi-sampling rate approach was applied as a further step to achieve an optimal performance. The theories underlining sound granulation, as a means of constructing complex sounds from grains, and the real-time implementation of this technique are outlined. The idea of sound granulation is quite similar to the quantum-wave theory, "acoustic quanta". Despite the conceptual simplicity, the signal processing requirements set tough demands, providing a challenge for this audio synthesis engine. Three issues arising from the results of the implementations above are discussed; the efficiency of the applications implemented, provisions for new processors and an optimal network architecture for sound synthesis

One Tone, Two Ears, Three Dimensions: An investigation of qualitative echolocation strategies in synthetic bats and real robots

Institute of Perception, Action and BehaviourThe aim of the work reported in this thesis is to investigate a methodology for studying perception by building and testing robotic models of animal sensory mechanisms. Much of Artificial Intelligence studies agent perception by exploring architectures for linking (often abstract) sensors and motors so as to give rise to particular behaviour. By contrast, this work proposes that perceptual investigations should begin with a characterisation of the underlying physical laws which govern the specific interaction of a sensor (or actuator) with its environment throughout the execution of a task. Moreover, it demonstrates that, through an understanding of task-physics, problems for which architectural solutions or explanations are often proposed may be solved more simply at the sensory interface - thereby minimising subsequent computation. This approach is applied to an investigation of the acoustical cues that may be exploited by several species of tone emitting insectivorous bats (species in the families Rhinolophidae and Hipposideridae) which localise prey using systematic pinnae scanning movements. From consideration of aspects of the sound filtering performed by the external and inner ear or these bats, three target localisation mechanisms are hypothesised and tested aboard a 6 degree-of-freedom, binaural, robotic echolocation system.In the first case, it is supposed that echolocators with narrow-band call structures use pinna movement to alter the directional sensitivity of their perceptual systems in the same whay that broad-band emitting bats rely on pinnae morphology to alter acoustic directionality at different frequencies.Scanning receivers also create dynamic cues - in the form of frequency and amplitude modulations - which very systematically with target angle. The second hypothesis investigated involves the extraction of timing cues from amplitude modulated echo envelopes

Research and technology

As the NASA Center responsible for assembly, checkout, servicing, launch, recovery and operational support of Space Transportation System elements and payloads, Kennedy Space Center is placing emphasis on its research and technology program. In addition to strengthening those areas of engineering and operations technology that contribute to safer, more efficient, and more economical execution of our current mission, we are developing the technological tools needed to execute the Center's mission relative to future programs. The Engineering Development Directorate encompasses most of the laboratories and other Center resources that are key elements of research and technology program implementation, and is responsible for implementation of the majority of the projects in this Kennedy Space Center 1988 Annual Report

Towards Solving the Dopamine G Protein Coupled Receptor Modelling Problem

The overall aim of this work has been to furnish a model of the dopamine (DA) receptor D2. There are currently two sub-groups within the DA family of G protein coupled receptors (GPCRs): D1 sub-group (includes D1 and D5) and the D2 sub-group (includes D2, D3 and D4). Organon (UK) Ltd. supplied a disk containing the PDB atomic co-ordinates of the integral membrane protein bacteriorhodopsin (bRh; Henderson et al., 1975 and 1990) to use as a template to model D2 - the aim being to generate a model of D2 by simply mutating the side-residues of bRh. The assumption being that bRh had homology with members of the supergene class of GPCRs. However, using the GCG Wisconsin GAP algorithm (Devereux et al., 1984) no significant homology was detected between the primary structures of any member of the DA family of GPCRs and bRh. However, given the original brief to carry out homology modelling using bRh as a template (see appendix 1) I felt obliged to carry out further alignments using a shuffling technique and a standard statistical test to check for significant structural homology. The results clearly showed that there is no significant structural homology, on the basis of sequence similarity, between bRh and any member of the DA family of GPCRs. Indeed, the statistical analysis clearly demonstrated that while there is significant structural homology between every catecholamine binding GPCR, there is no structural homology what so ever between any catecholamine binding GPCR and bRh. Hydropathy analysis is frequently used to identify the location of putative transmembrane segments. However, is difficult to predict the end positions of each ptms. To this end a novel alignment algorithm (DH Scan) was coded to exploit transparallel supercomputer technology to provide a basis for identifying likely helix end points and to pinpoint areas of local homology between GPCRs. DH Scan clearly demonstrated characteristic transmembrane homology between different subtype DA GPCRs. Two further homology algorithms were coded (IH Scan and RH Scan) which provided evidence of internal homology. In particular IH Scan independently revealed a repeat region in the 3rd intracellular loop (iIII) of D4 and RH Scan revealed palindromic like short stretches of amino acids which were found to be particularly well represented in predicted ?-helices in each DA receptor subtype. In addition, the profile network prediction algorithm (PHD; Rost et al., 1994) predicted a short alpha-helix at greater than 80% probablility at each end of the third intracellular loop and between the carboxy terminal end of transmembrane VII and a conserved Cys residue in the forth intracellular loop. Fourier analysis of catecholamine binding GPCR primary structures in the form of a multiple-sequence file suggested that the consensus view that only those residues facing the protein interior are conserved is not entirely correct. In particular, transmembrane helices II and III do not exhibit residue conservancy characteristic of an amphipathic helix. It is proposed that these two helices undergo a form of helix interface shear to assist agonist binding to a Asp residue on helix II. This data in combination with information from a number of papers concerning helix shear interface mechanism and molecular dynamic studies of proline containing ?-helices suggested a physically plausible binding mechanism for agonists. While it was evident that homology modelling could not be scientifically justified, the combinatorial approach to protein modelling might be successfully applied to the transmembrane region of the D2 receptor. The probable arrangement of helices in the transmembrane region of GPCRs (Baldwin, 1993) which was based on a careful analysis of a low resolution projection map of rhodopsin (Gebhard et ah, 1993) was used as a guide to model the transmembrane region of D2. The backbone torsion angles of a helix with a middle Pro residue (Sankararamakrishnan et al., 1991) was used to model transmembrane helix V. Dopamine was successfully docked to the putative binding pocket of D2. Using this model as a template, models of D3 and D4 were produced. A separate model of Di was then produced and this in turn was used as a template to model D5