Thesis (MScEng)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: Pleural effusion is a common respiratory condition that is characterized by an abnormal collection of fluid in the lung cavity. In this study, an innovation using the transmission of sound into the respiratory system as a novel tool to detect fluid in the lung was developed. First, the method was evaluated on a phantom model of a lung. Based on the results of this test model, the appropriate technique was used in a clinical study. This method has several advantages, such as that is non-invasive, low cost, and easy for clinical review. Two techniques, including analysis of the frequency response of the model and the transient time of transmitted sound in the lung, were evaluated in the phantom models of the human lung. Two phantom models with similar geometry to the human lung, including a healthy model (without fluid in the model) and a pleural effusion model (with bulk of fluid in the model) were developed. These models have acoustical properties similar to the lung parenchyma. To obtain the frequency responses of the model, a sine sweep signal was transmitted into the model and the frequency response of the model was then calculated using the fast Fourier transform. The transient time of the transmitted sound was calculated using a cross correlation method. The results show that the locations of fluid in the model were detectable using both techniques. However, the transient time technique is better than the frequency response technique because it is simple, fast, and has potential for use in a clinical enviorment. Based on the results obtained from the phantoms, the transient time method was performed on both 22 healthy participants and four patients diagnosed with pleural effusion. To perform this technique on human subjects, a data acquisition system was developed. Two types of sound, including a complex chirp sound and a polyphonic sound, were transmitted into the respiratory systems of the participants. The time delay between a reference microphone, located on the trachea of the subject, and eight microphones attached to the chest was computed using a cross correlation method, and the effect of inhalation and lung size on the transient time of transmitted sound on the healthy subject was evaluated. The results show that using transmission of sound in the lung is a promising technique in the diagnosis of pleural effusion. / AFRIKAANSE OPSOMMING: Pleurale effusie is 'n algemene respiratoriese toestand wat gekenmerk word deur 'n abnormale versameling van vloeistof in die longholte. In hierdie studie is 'n innoverende manier ontwikkel om vloeistof in die long met behulp van die transmissie van klank te bespeur. Die metode is eers op 'n fantoommodel van 'n long geëvalueer. Op grond van die resultate van hierdie toetsmodel is die geskikte tegniek in 'n kliniese studie gebruik. Hierdie metode het verskeie voordele, soos dat dit ingreepsvry is, nie duur is nie en kliniese evaluering moontlik maak. Twee tegnieke, naamlik ontleding van die frekwensierespons van die model en die oorgangstyd van versende klank in die long, is in die fantoommodel van die menselong geëvalueer. Twee fantoommodelle met soortgelyke geometrie aan die menselong, met inbegrip van 'n gesonde model (sonder vloeistof in die model) en 'n pleurale-effusie-model (met 'n massa vloeistof in die model), is ontwikkel. Hierdie modelle het akoestiese eienskappe soortgelyk aan die longparenchiem. Om die frekwensieresponse van die model te verkry, is 'n sinuskrommesein tot in die model versend. Die frekwensierespons van die model is met behulp van die vinnige Fourier-transformasie bereken. Die oorgangstyd van die versende klank is deur 'n kruiskorrelasie-metode bereken. Die resultate toon dat die ligging van die vloeistof in die model met albei tegnieke bespeur kan word. Die oorgangstyd-tegniek is egter beter as die frekwensierespons-tegniek, aangesien dit eenvoudig en vinnig is en maklik in 'n kliniese omgewing gebruik kan word. Op grond van die resultate wat van die fantome verkry is, is die oorgangstyd-metode op 22 gesonde deelnemers en vier pasiënte wat met pleurale effusie gediagnoseer is, uitgevoer. 'n Dataverkrygingstelsel is ontwikkel ten einde hierdie tegniek op proefpersone uit te voer. Twee soorte klank, naamlik 'n komplekse tjirpgeluid en 'n polifoniese klank, is na die respiratoriese stelsels van die deelnemers versend. Die tydvertraging tussen 'n verwysingsmikrofoon in die tragea van die proefpersoon en agt mikrofone wat aan die bors vasgeheg is, is met 'n kruiskorrelasie-metode bereken, en die uitwerking van inaseming en longgrootte op die oorgangstyd van versende klank op die gesonde proefpersone is geëvalueer. Die resultate toon dat die gebruik van transmissie van klank in die long 'n belowende tegniek vir die diagnose van pleurale effusie is.