Thesis (MSc (Physiology))--University of Stellenbosch, 2000. / 251 leaves single sided printed, preliminary pages and numbered pages 1-151. Includes bibliography, list of appendixes, abbreviations, variables, figures and tables. Digitized at 300 dpi (OCR), using a Bizhub 250 scanner. / ENGLISH ABSTRACT: The Whistle Watch™, an innovative and commercialised peak flow monitor, inspired this study, with its abnormal and complex measuring behaviour. The Whistle Watch™ latter is an audible peak flow monitor with a threshold-activated whistle as the essential component. The whistle is calibrated for a certain flow, and then encased in a body with a variable exhaust valve to atmosphere. Using the Whistle Watch™, with the exhaust valve pre-set, executing a forced expiratory effort, the audible notification of the whistle would indicate a stable asthmatic condition at that setting. No audible notification would result in the use of medication as a preventative measure. Due to the absence of existing theories and literature on the mechanics of whistles, the Whistle Watch™ was empirically developed. This study therefore, focuses on the characterisation and consequent improved understanding ofthe mechanics ofa whistle, with the objective to monitor pulmonary function in a novel way. During this study, a novel technique was developed to determine the reed activation point, or onset of oscillation, in terms of pressure. This technique was then implemented throughout the study. The initial observation and experimentation underlined the whistle's activation sensitivity towards any irregularities of the reed surface. A statistical spread of reed activation pressures defined the reed's inherent non-linear properties. A high dependence of reed activation towards upstream geometry was noted, and a clarification hypothesis was formulated. The effect of reed dimensions on activation pressure was exposed as a complex unexplored field. Existing mathematical reed theories only accommodate steady state oscillations, whereas the completed study indicated a high sensitivity of the reed activation pressure towards different input envelopes. This sensitivity was encapsulated in a mathematical model, with initial support and proofprovided by a previous independent study. All the observed effects and phenomena had far reaching practical application towards the production and quality control ofthe Whistle Watch™. / AFRIKAANSE OPSOMMING: Whistle Watch™, 'n inoverende, kommersieel piekvloeimonitor, was die inspirasie vir die studie, deur sy abnorrnale en ingewikkelde meet-gedragskenrnerke. Laasgenoemde is 'n piekvloeimonitor met 'n fluit wat geaktiveer word by 'n vooraf vasgestelde drempel. Die fluit word gekalibreer vir 'n bepaalde vloei, waarna dit geenkapsuleer word in 'n hoofdeel met 'n veranderlike uitlaat na die atmosfeer. By die gebruik van die Whislte Watch™, met die uitlaatklep gestel op 'n voorafbepaalde vloeitempo, word 'n bepaalde ekspirasievlak verkry. Hierdie vlak het 'n hoorbare kennisgewing tot gevolg, wat 'n stabiele asmatiese toestand aandui. In die afwesigheid van 'n hoorbare respons, word medikasie as voorkornende rnaatreel vereis. Die Whislte Watch™ is empiries ontwikkel in die afwesigheid van bestaande teoriee en literatuur ten opsigte van die werking van fluite. Die fokus van hierdie studie word dus geplaas op die karakterisering van die werking van fluite, wat 'n beter begrip tot gevolg het. 'n Nuwe benadering tot die monitering van die pulrnonere funksie is dus haalbaar. Tydens die studie is 'n unieke tegniek ontwikkel om die aktiveringspunt van die riet, of die aanvang van ossilasie in terrne van druk, te bepaal. Hierdie tegniek is toe dwarsdeur die studie geiinplimenteer. Die fluit se aktiveringssensitiwiteit, in terrne van die oppervlak-onreelmatighede, van die riet was duidelik waarneembaar. Die inherente nie-liniere eienskappe van die riet is duidelik waarneembaar in rietaktiveringsdrukke. 'n Verklarende hipotese is as gevolg van 'n afhanklikheid van die rietaktiveringsdrukke relatief tot stroom-op geometrie, gestel. Die effek wat rietafinetings op aktiveringsdrukke het, was blootgel~ as 'n komplekse onontwikkelde gebied. Bestaande wiskundige rietteoriee maak slegs voosiening vir nie-fluktuerende ossilasies. Na voltooiing van hierdie studie is dit duidelik dat daar wei 'n hoe sensitiwiteit van die rietaktiveringsdrukke bestaan, met verwysing na verskillende ekspiratoriese profiele. Hierdie sensitiwiteit word vervat in 'n wiskundige model met toepaslilke ondersteuning en bewyse uit 'n vorige, onathanklike studie. Aile waarneembare phenomena het resulterende praktiese impakte ten opsigte van die produksie en gehalteversekering van die Whistle Watch™.