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Purpose: An open mouth approach is used in voice therapy for enhancing speech and voice production and relaxing the laryngeal musculature. The acoustic and physiological consequences of an open jaw posture, however, have not been clearly understood due to a paucity of cross-system studies taking the age effect into consideration. The major aims of this study are twofold (1) to examine if the geriatric voice may be improved using an “open jaw” posture and (2) if an aging effect on the voice of normal healthy adults can be detected through acoustic and physiological measures Method: The main part of this study involved simultaneous multi-channel voice recordings obtained from 85 healthy adults aged between 38 and 93 years. A convenience sampling strategy was used to recruit at least five females and five males in each of four age groups, 35-59 years (35+), 60-69 (60+), 70-79 (70+), and above 80 (80+). For simultaneous acoustic, electroglottographic (EGG), and jaw displacement recordings, participants were asked to perform two tasks which included a sustained vowel task and a sentence production task. The sustained vowel task involved sustaining the vowel /a/ in five different conditions, an isolated vowel /a/ produced at normal, low, and high pitch levels and the vowel /a/ initiated with a consonant (/m/ and /h/). The sentence production task involved production of the sentence 'We saw two cars,' containing the vowels /i, ɔ, u, a/. For simultaneous airflow-EGG recordings, participants were asked to sustain the vowel /a/ at normal pitch. For simultaneous airflow-air pressure-EGG recordings, participants were asked to repeat /pa/ five times in one breath. Participants were asked to perform all of the tasks using two jaw postures (normal and open). A series of univariate analysis of variances were used to identify instrumental measures sensitive for discriminating between the four age groups and the two jaw postures. A follow-up perceptual study was conducted to determine the effect of an open jaw posture on vowel intelligibility and voice clarity. A quota sampling strategy was used to recruit 40 normal hearing participants, including 20 females (age range = 18-42 years, mean = 25.3, SD = 7.9) and 20 males (age range = 18-47, mean = 23.6, SD = 6.7). These listeners were presented with vowels segmented from the sentences recorded in the first experiment and asked to perform a vowel identification and a voice clarity discrimination task. The vowel samples were taken from 40 speakers, with five females and five males in each of the four age groups (35+, 60+, 70+, and 80+). The percentages of correct vowel identification for voices produced with normal and open jaw postures were compared. The percentages of vowels judged as 'clearer' in a normal-open jaw contrast pairs were also calculated for comparison. Results: Significant age group effects were found in this study for both genders on fundamental frequency (F0), voice onset time (VOT) (/ka/), open quotient (OQ), and speed quotient (SQ), with additional age differences detected for females on %jitter, %shimmer, signal-to-noise ratio (SNR), and the second formant frequency (F2), and for males a significant age group effect was found on VOT (/tu/). Results for both females and males revealed significant open jaw posture effects on F0, F2, VOT (/ka/), MFR, SPL and vowel space area. In addition, for females significant posture effects were found on F1, subglottal pressure and the H1-H2 amplitude difference, and for males, significant posture effects were found on %jitter and VOT-/tu/. Results from the follow-up perceptual study revealed that an open jaw posture was associated with better vowel identification and better voice clarity. Conclusions: A selection of instrumental measures was shown to be useful for detecting voice changes due to aging. Instrumental and perceptual evidence was found that an open jaw posture was associated with positive changes in vocal behaviours, including improved phonatory stability, vocal power, and voice clarity.

Combined Electric-acoustic stimulation (EAS) is becoming an increasingly viable treatment option for individuals with sloping severe to profound high frequency hearing loss and residual low frequency hearing. Sound stimulation via EAS is delivered to the high frequency region electrically using cochlear implantation, and to the low frequency region acoustically with or without amplification from hearing aids. This combined mode of stimulation often results in improved speech recognition in background noise compared to either mode of stimulation in isolation. It is important to note that many EAS listeners have some degree of hearing loss in the low frequency region, and may experience associated effects such as reduced frequency selectivity and elevated audiometric thresholds. This study simulated EAS listening in 20 normal hearing listeners by combining vocoded high frequency sound with low frequency sound. Low frequency sound was further manipulated by applying varying degrees of spectral smearing and attenuation to the low frequency region in an EAS simulation, to simulate changes in frequency selectivity and sensitivity that usually accompany sensorineural hearing loss. The aim of this study was to investigate the effects of spectral smearing and attenuation of low frequency information on the identification of vocoded speech in noise. Participants were required to complete a sentence recognition task in the presence of competing talkers for six simulated listening conditions with varying degrees of processing in the low frequency region. Results indicated that the advantage for speech in noise of simulated combined EAS over simulated electric stimulation alone was 3.9 dB when low frequency sound was unprocessed, 2.9 dB when low frequency sound had spectral smearing of x3 applied, and 2.4 dB when low frequency sound had spectral smearing of x6 applied. When 30 dB attenuation was applied as well as x3 spectral smearing, no significant benefit was observed. When 60 dB attenuation was applied as well as x3 spectral smearing, a significant negative relationship was found, with a 3 dB disadvantage found for simulated EAS compared to simulated electric stimulation alone. Overall, the results of this study indicate that there is indeed a significant improvement in speech recognition in a background of competing speakers with simulated EAS compared to simulated electric stimulation only. However, when reduced hearing thresholds were simulated for the residual low frequency hearing, we found that this benefit was either absent or reversed. These results therefore support the use of amplification for individuals with reduced hearing thresholds in the low frequencies in order to utilize the benefit they are able to achieve with combined EAS.

Corticosteroids are the most potent and reliable of the available agents among the anti-inflammatory drugs, and have assumed a major role in the management of asthma. This has subsequently resulted in the global widespread use of inhaled corticosteroids (ICS). A variety of studies have been undertaken to examine the effects of ICS on voice production among people with asthma. Most research suggests that the long-term use of ICS has a negative effect on voice production. However, the results of these studies are limited because of the reliance upon examining an asthmatic population and not consistently recording the dose prescribed. As a result, one cannot exclude that some of the voice problems may have been previously caused by asthma and thus, the contributing effects of ICS are obscured. Therefore, an ideal approach to examine the influence of ICS on voice is to test its short-term effects on healthy individuals, using a specific ICS (Fluticasone Propionate) at a fixed dose (1000 µg/Day). Thirty healthy adults (15 females & 15 males) aged between 18 to 30 years participated in this study. All participants were non-smokers with no history of speech, language or voice disorder. No participants had a history of asthma, respiratory illness hospital admission or inhaler use within the past 3 months. All participants followed the treatment regime often prescribed by physicians (in Canterbury region) for treating asthma (500 µg in morning & 500 µg in evening). Each participant self administered (inhaled) two puffs of ICS in the morning and again in the evening over a six day period. Voice samples were audio-recorded prior to undergoing the ICS regime, at various points during the ICS regime, and at the conclusion of ICS regime. Each participant’s audio-recorded samples were submitted for acoustic analysis using a commercially available speech analysis system (CSL 4300B, Kay Elemetrics, 1994). Three measures were performed, (1) vocal fundamental frequency (F0), (2) long-time spectral analysis (LTAS) and (3) formant frequency and formant frequency bandwidth. The results of this study indicate that ICS does have an effect on acoustic properties of voice. These effects were more evident in connected speech compared to isolated vowel productions. In particular, the spectral tilt and first spectral peak of continuous speech samples were found to change from baseline. The current results are discussed in regard to the phonatory deterioration associated with ICS use. The present study provides a framework for developing ICS treatment for respiratory disease in the phase of minimizing adverse effects on voice.

Wireless Surface Acoustic Wave (SAW) devices were fabricated and tested using planar Lithium Niobate (LiNbO₃) as substrate. The working frequencies were in the 180 MHz and 360 MHz range. Using a network analyser, the devices were interrogated with a wireless range of more than 2 metres. Trials with Electron Beam Lithography (EBL) to fabricate SAW devices working in the 2450 MHz with a calculated feature size of 350 nm are discussed. Charging problems became evident as LiNbO₃ is a strong piezoelectric and pyroelectric material. Various attempts were undertaken to neutralise the charging problems. Further investigation revealed that sputtered Zinc Oxide (ZnO) is a suitable material for attaching SAW devices on irregularly shaped material. DC sputtering was used and several parameters have been optimised to achieve the desired piezoelectric effect. ZnO was sputtered using a magnetron sputtering system with a 75 mm Zn target and a DC sputter power of 250 Watts. Several trials were performed and an optimised material has been prepared under the following conditions: 9 sccm of Oxygen and 6 sccm of Argon were introduced during the process which resulted in a process pressure of 1.2x10⁻² mbar. The coatings have been characterised using Rutherford Backscattering, X-ray diffraction, SEM imaging, and Atomic force microscopy. SAW devices were fabricated and tested on 600 nm thick sputtered ZnO on a Si substrate with a working frequency of 430 MHz. The phase velocity has been calculated as 4300m/s. Non-planar samples have been coated with 500 nm of sputtered ZnO and SAW structures have been fabricated on using EBL. The design frequency is 2450 MHz, with a calculated feature size of 1 µm. The surface roughness however prevented a successful lift-off. AFM imaging confirmed a surface roughness in the order of 20 nm. Ways to improve manufacturability on these samples have been identified.

The ability to determine wood quality using non-destructive tests has enormous potential for the forestry industry in both research and commercial applications. This thesis describes some of the theory of acoustic waves in wood and how wood stiffness can be estimated by measuring the velocity of acoustic waves. Attention is paid to both resonance and stress wave timer technologies and the benefits and problems with both. A detailed description is given of the design of a new tool (Treetap 5.0) to aid in future, acoustic based, timber inspection research.

I recorded acoustic and visual components of Indian Peafowl (Pavo cristatus) mating displays at the Assiniboine Park Zoo, in Winnipeg, Manitoba, Canada. I determined that males produce infrasound (<20 Hz) in their train displays, and documented responses of peafowl to playbacks of both audible and infrasonic components of their vocalizations and train displays. Peafowl responded to infrasonic signals by increasing alertness and locomotory behaviours, while males also responded by calling. In response to audible call playbacks, males called and faced the playback unit while females increased locomotion and alertness, though peafowl did not respond to audible signal components from the train display, suggesting that infrasonic components constitute the essential signal component within those displays. Beyond revealing a critical role of acoustic signals in modulating interactions among peafowl, my results provide the first empirical evidence of a bird producing and perceiving infrasound as a signal.

I recorded acoustic and visual components of Indian Peafowl (Pavo cristatus) mating displays at the Assiniboine Park Zoo, in Winnipeg, Manitoba, Canada. I determined that males produce infrasound (<20 Hz) in their train displays, and documented responses of peafowl to playbacks of both audible and infrasonic components of their vocalizations and train displays. Peafowl responded to infrasonic signals by increasing alertness and locomotory behaviours, while males also responded by calling. In response to audible call playbacks, males called and faced the playback unit while females increased locomotion and alertness, though peafowl did not respond to audible signal components from the train display, suggesting that infrasonic components constitute the essential signal component within those displays. Beyond revealing a critical role of acoustic signals in modulating interactions among peafowl, my results provide the first empirical evidence of a bird producing and perceiving infrasound as a signal.