Studies of speech perception indicate that it is more difficult for people with and without hearing loss to detect speech in noise. Functional communication in noise, however, has been less often studied; there is currently no well-designed measure of communication effectiveness. The Diapix Task (Baker & Hazan, 2011) has potential; it elicits dialogue by having two people converse to find differences between two pictures. The purpose of the present study was to develop a reliable measure of communication effectiveness and use this measure to determine how noise influences communication. Experiment 1 investigated use of the Diapix Task as a measure of communication effectiveness in noise. Seven young adults with normal hearing, paired with an assistant, completed the Task with three different picture pairs in a sound field of cafeteria noise. Communication effectiveness was measured by counting communication breakdowns. Results indicated that the Task did elicit breakdowns and, out of nine picture pairs, one elicited a different amount of breakdowns than the others; this pair was excluded. Experiment 2 used the Diapix Task to measure communication effectiveness in quiet and different types of noise. Relation between self-reported use of communication strategies and communication effectiveness was also explored. Fourteen young adults with normal hearing completed the Diapix Task with an assistant in three conditions: quiet, cafeteria noise, and competing dialogue. Results indicated that significantly more breakdowns occurred in noise than quiet, but that there was no significant difference between types of noise. Additionally, self-reported use of communication strategies did not correlate with communication effectiveness. Results support use of the Diapix Task as a functional measure of communication effectiveness in young adults with normal hearing; future research should investigate use of the Diapix Task to measure communication effectiveness in clinical populations.

Noise in a fluid system can be treated with a prototypical liner-style suppressor, an expansion chamber which includes an internal annulus of syntactic foam. A syntactic foam liner consists of host material with hollow microspheres which collapse under pressure to add compliance to the suppressor. The liner effectively increases the transmission loss of the suppressor, or ratio between inlet and outlet acoustic energy. Currently, liner-style suppressors are not commercially available. This study investigates the integration of solid liner material within suppressor shells while also analyzing the effect of flow-smoothing diffusors on the transmission loss of the suppressor. The diffusors function to center the liner within the device, while reducing the potential for turbulence-induced self-noise. The diffusor may also impact the longevity of the liner, by reducing mechanical erosion. The results of the study provide additional insight to the commercial viability of the liner-style suppressor.

International Telemetering Conference Proceedings / October 22-25, 2001 / Riviera Hotel and Convention Center, Las Vegas, Nevada / Today’s telemetry specifications are requiring electronic systems to not only survive, but operate through severe dynamic environments. Pyrotechnic shock and Random Vibration are among these environments and have proven to be a challenge for systems that rely on highly stable, low phase noise signal sources. This paper will mathematically analyze how Pyrotechnic shock and Random Vibration events deteriorate the phase noise of crystal oscillators (XO).

Thesis (PhD) -- Stellenbosch University, 2004. / Some digitised pages may appear illegible due to the condition of the original hard copy. / ENGLISH ABSTRACT: The radio noise (RN) performance of an AC high voltage transmission line is a determining factor when accessing the reliability of the design. The conducted RN level across the terminals of a PLC receiver, used in the teleprotection system of the line, is of particular concern. In this dissertation, existing empirical and semi-analytical RN prediction methods are evaluated by comparing the conducted RN levels of four South African lines to the predicted levels. Existing RN measurement protocols are consolidated and a new RN measurement protocol is proposed for the comparison. A prediction methodology, based on the EdF, EPRI and IREQ semi-analytical methods, is formulated. The semi-analytical methods are not able to accurately predict the variation of the conducted RN with frequency in the PLC band, nor are they able to predict the RN performance of short lines. A wideband excitation function, which considers the statistical characteristics of the measured RN pulse train, is therefore proposed in this dissertation. Having investigated the extraction of this excitation function from ESKOM’s Megawatt Park corona cage, it is concluded that a small corona cage is required. The design of a small cage is presented and the extraction of the excitation function is described. Attention is given to assessing the effect of changes in space charge distributions. The effect of space charge collision with an insulated cage on the extracted pulse parameters is linear, provided space charge diffusion is negligible. The onset streamer, positive streamer and negative streamer corona modes were identified as the only modes with measurable RN in the frequency regime 150 kHz to 30 MHz. Formulas are derived for the prediction of the inception gradients for these modes. The RN performance of an ACSR Hare conductor is extracted from the small cage. The RN performance of the Acacia-Koeberg line is also approximated in the PLC band. The dissertation concludes that the proposed wideband excitation function method is capable of accurately predicting the variation of RN levels with frequency. It can also be used to predict the RN performance of short line sections, as well as the relationship between RMS, QP and average RN levels from a transmission line. / AFRIKAANSE OPSOMMING: Die korona-werkverrigting van ‘n WS hoogspanningstransmissielyn het belangrike gevolge vir die betroubaarheid van die ontwerp van die lyn. Die geleide radioruis (RR) vlak op die kraglyndragolf kommunikasie sisteem, wat vir tele-beveiliging gebruik word, is veral van belang. In hierdie werkstuk word bestaande metodes gebruik om die korona-werkverrigting te bepaal en dan met gemete waardes van vier Suid Afrikaanse lyne te vergelyk. Bestaande RR meetmetodes word saamgevat en ‘n nuwe metingsprotokol word voorgestel om resultate te vergelyk. Na aanleiding van hierdie vergelykings word ‘n tegniek ontwikkel om die RR van ‘n lyn te voorspel. Hierdie tegniek gebruik die EdF, EPRI en IREQ metodes. Die voorgestelde tegniek kan nie die verandering van die RR met frekwensie bepaal nie. Dit kan ook nie die RR van kort lyne bepaal nie. ‘n Wyeband RR bron word dus voorgestel. Nadat ESKOM se Megawatt Park korona-kou ondersoek is, is die gevolgtrekking gemaak dat ‘n klein koronakou die nodige wyeband RR bron sal voorsien. Ruimtelading bots met die klein korona-kou. Die effek van hierdie botsings op die pulsparameters is lineer indien ladingsdiffusie nie plaasvind nie. Die aanvangs, positiewe en negatiewe kanaalontladings (“streamers”) is identifiseer as die enigste koronamodusse wat RR veroorsaak tussen 150 kHz en 30 MHz. Die spanning waarby hierdie modusse voorkom, is bepaal. Die korona-werkverrigting van ‘n “ACSR Hare” geleier is bepaal. Die korona-werkverrigting van die Acacia-Koeberg transmissie lyn is ook gekwantifiseer by die kraglyn-dragolf kommunikasie frekwensies. Die wyebandbron metode kan die verandering in RR met frekwensie goed voorspel. Die nuwe metode kan ook gebruik word om die RR van kort lyne te bepaal, asook die verband tussen RMS, QP en gemiddelde RR vlakke.

Thesis (DComm)--Stellenbosch University, 1976. / AFRIKAANSE OPSOMMING: sien item vir volteks. / ENGLISH ABSTRACT: see item for full text

Understanding speech in noisy environments is a challenge for normal-hearing and impaired-hearing listeners alike. However, it has been shown that speech intelligibility can be improved in these situations using a strategy called the ideal binary mask. Because this approach requires knowledge of the speech and noise signals separately though, it is ill-suited for practical applications. To address this, many algorithms are being designed to approximate the ideal binary mask strategy. Inevitably though, these algorithms make errors, and the implications of these errors are not well-understood. The main contributions of this thesis are to introduce a new framework for investigating binary masking algorithms and to present listener studies that use this framework to illustrate how certain types of algorithm errors can affect speech recognition outcomes with both normal-hearing listeners and cochlear implant recipients.

ITC/USA 2011 Conference Proceedings / The Forty-Seventh Annual International Telemetering Conference and Technical Exhibition / October 24-27, 2011 / Bally's Las Vegas, Las Vegas, Nevada / New developments in miniaturized integrated film bulk acoustic resonator (FBAR) filters and low noise amplifiers have resulted in the possibility of extremely small integrated antenna, filter, and low noise amplifier subsystems for use in airborne telemetry (TM) systems. This paper gives examples of a new development in airborne GPS antennas using an integrated band pass FBAR filter and low noise amplifier. Data is also included on the example antenna in a GPS/TM system.

published_or_final_version / Electrical and Electronic Engineering / Doctoral / Doctor of Philosophy

published_or_final_version / Mechanical Engineering / Doctoral / Doctor of Philosophy

published_or_final_version / Speech and Hearing Sciences / Master / Master of Science in Audiology