The sound of 1-bit:technical constraint and musical creativity on the 48k Sinclair ZX Spectrum

This article explores constraint as a driver of creativity and innovation in early video game soundtracks. Using what was, perhaps, the most constrained platform of all, the 48k Sinclair ZX Spectrum, as a prism through which to examine the development of an early branch of video game music, the paper explores the creative approaches adopted by programmers to circumvent the Spectrum’s technical limitations so as to coax the hardware into performing feats of musicality that it had never been designed to achieve. These solutions were not without computational or aural cost, however, and their application often imparted a unique characteristic to the sound, which over time came to define the aesthetic of the 8-bit computer soundtrack, a sound which has been developed since as part of the emerging chiptune scene. By discussing pivotal moments in the development of ZX Spectrum music, this article will show how the application of binary impulse trains, granular synthesis, and pulse-width modulation came to shape the sound of 1-bit music

Investigation of the quality of umbilical artery Doppler waveforms

In Doppler systems which automatically calculate the maximum frequency envelope and pulsatility index (PI) of umbilical artery Doppler waveforms there is the possibility of error in these parameters when the technical quality of the acquired waveform is low. Low quality waveforms may arise when there is an inappropriate set of physical parameters or when there are other sources of noise such as overlying vessels signals. In this thesis the effect of physical parameters on the envelope and on PI are investigated, and also methods for the detection of low quality waveforms are described and tested. A flow phantom which is able to produce realistic looking umbilical artery Doppler waveforms is described. This is based upon microcompruter control of a stepping motor / gear pump combination. The statistics of the Doppler spectra produced using artificial blood and human blood in the phantom are found to be identical. The effect of a number of physical parameters on the simulated umbilical artery waveforms produced using the phantom is investigated. The accuracy of estimation of the envelope and the PI is similar over a wide range of physical conditions. A suitable image processing algorithm for speckle reduction of Doppler waveforms is developed and tested using simulated waveforms from the phantom. Using the flow device it was found that both filtering of the envelope and also speckle suppression of the spectrum improved the accuracy of estimation of the envelope and of the PI. A number of quality indices based upon the degree of noise of the envelope are described. Using the flow device there is found to be a high correlation between the quality index values, and the errors in PI and errors in envelope estimation respectively. In a clinical trial the quality index values from umbilical arteries were compared with the waveform quality as assessed by a skilled observer. The clinical results show that quality indices are able to separate high and low quality waveforms when the indices are calculated from the unprocessed envelope, but not when calculated from the filtered envelop

Synthetic aperture sonar

Synthetic aperture techniques have been applied very successfully for many years in astronomy and radar to obtain high resolution images, an outstanding example in recent years being the use in remote sensing satellite systems. In underwater acoustics, because of the inherent problems caused by random fluctuations in the signal path, the slow velocity of the acoustic wave and the unknown movements of the transducer as it traverses the aperture, the application of the synthetic aperture technique has mainly been limited to the very useful but rather inferior non-coherent technique known as side-scan sonar. However the rapid advances that are being made in micro-chip technology and fast digital signal processing, and the development in image processing algorithms has created renewed interest in the possible application of the synthetic aperture technique to underwater acoustics. This thesis describes such a study

A study of digital sampling in gnathosonics

The purpose of this study has been to provide clinicians with a simple low cost system for gnathosonic investigation in the dental surgery, instead of referring patients to specialist centres. Hitherto the literature describing the sounds made by occlusion of the teeth has offered many conflicting hypotheses as to the relationship between the sounds produced and the condition of the gnathic system. Many techniques developed to investigate factors involved in tooth vibration or impact are cumbersome and time consuming. The simple system developed in this work is based on fast digital capture using an inexpensive microcomputer of a type commonly found in the home. Specific software has been developed to capture and manipulate the transient signals generated by tooth and other impacts. As part of the study the software has been rigorously verified for timings, frequency limits and program errors, and has been validated using both mathematically generated and other control signals such as those provided by a signal generator. The system has been used both in vitro and in vivo to investigate the manner in which shock waves from tooth impacts are received after transmission through the body structures. A meaningful interpretation of the data recorded has been established, although it has had to be accepted that scientific analysis of shock wave propagation through tissue requires further investigation and is beyond the scope of this work. In addition to sounds generated by occlusion of the teeth, sounds made by the percussion of implants set into the maxilla and mandible have also been recorded, on the assumption that serial recordings taken from the time of insertion could indicate integration or give early warning of failure. The technique of digital signal capture has been applied elsewhere in the body, for example sounds made by both natural and artificial joints. This limited study indicates that the developed system may have much wider application than gnathosonic measurement alone. It is suggested that the differing results of many researchers into gnathosonics may be due to lack of standardisation of the sensors and other equipment employed, and to misinterpretation of the sound recordings of the occlusion of the teeth. It is proposed that certain parameters should be established in the field of gnathosonics, particularly in regard to the sensors and recording apparatus. It is only then that the results from serial sessions, and the work of different investigators will stand comparison

Rescuing the legacy project: a case study in digital preservation and technical obsolescence

The ability to maintain continuous access to digital documents and artifacts is one of the most significant problems facing the archival, manuscript repository, and record management communities in the twenty-first century. This problem with access is particularly troublesome in the case of complex digital installments, which resist simple migration and emulation strategies. The Legacy Project, which was produced by the William Breman Jewish Heritage Museum in Atlanta, was created in the early 2000s as a means of telling the stories of Holocaust survivors who settled in metropolitan Atlanta. Legacy was an interactive multimedia kiosk that enabled museum visitors to read accounts, watch digital video, and examine photographs about these survivors. However, several years after Legacy was completed, it became inoperable, due to technological obsolescence. By using Legacy as a case study, I examine how institutions can preserve access to complex digital artifacts and how they can rescue digital information that is in danger of being lost.M.S.Committee Chair: Knoespel, Kenneth; Committee Member: Burnett, Rebecca; Committee Member: Fox Harrell; Committee Member: TyAnna Herringto

Development of a gated optical multichannel analyser for laser-plasma spectroscopy

An Optical Multichannel Analyser (OMA) has been developed for the detection of radiation from laser-produced plasmas (LPPs). The system is based on a gated image - intensified photodiode array (PDA) Software for the control of, and data acquisition from, the OMA system has been developed. A high resolution (10ns) delay generator was also designed and constructed to permit timeresolved. optical spectroscopy. The system has been tested and operated with a laser plasma source m the visible and near infra-red (NIR) spectral region (400 -> 800nm) Some initial results from preliminary experiments to extend the usefulness of the OMA system into the vacuum-UV (VUV) are presented