The link to subjective parameters and objective parameters in the field of room acoustics has been the source of much research. This thesis surveys some of the available objective room acoustical analysis methods, quantify their advantages and disadvantages with respect to the measurement of acoustical qualities of professionally operated critical listing rooms, and implements these methods in a range of critical listening rooms. In conjunction with the objective room analysis, a subjective component of research was also performed. A series of anechoically recorded standard instrument sounds were presented to professional listeners in their critical listening spaces with the listeners asked to alter the sounds to taste: to

This dissertation is a continuation of the work by Zabolotskaya (Sov. Phys. Acoust. 32, 296-299 (1986)) and Wochner et al. (J. Acoust. Soc. Am. 125, 2488-2495 (2008)) on the nonlinear propagation of shear wave beams in an isotropic solid. In those works, a coupled pair of nonlinear parabolic equations was derived for the transverse components of the particle motion in a collimated shear wave beam, accounting consistently for the effects of diffraction, viscosity and nonlinearity. The nonlinearity includes a cubic nonlinear term that is equivalent to the nonlinearity present in plane shear waves, as well as a quadratic nonlinear term that is unique to diffracting beams. The purpose of this work is to investigate the quadratic nonlinear term by considering second-harmonic generation in Gaussian beams as a second-order nonlinear effect using standard perturbation theory. Since shear wave beams with translational polarizations (linear, elliptical, and circular) do not exhibit any second-order nonlinear effects, we broaden the class of source polarizations considered by including higher-order polarizations that account for stretching, shearing and rotation of the transverse plane. We find that the polarization of the second harmonic generated by the quadratic nonlinearity is not necessarily the same as the polarization of the source-frequency beam, and we are able to derive a general analytic solution for second-harmonic generation that gives explicitly the relationship between the polarization of the source-frequency beam and the polarization of the second harmonic. Additionally, we consider the focusing of shear wave beams with this broader class of source polarizations, and find that a tightly-focused, radially-polarized shear wave beam contains a highly-localized region of longitudinal motion at the focal spot. When the focal distance of the beam becomes sufficiently short, the amplitude of the longitudinal motion becomes equal to the amplitude of the transverse motion. This phenomenon has a direct analogy in the focusing properties of radially-polarized optical beams, which was investigated experimentally by Dorn et al. (Phys. Rev. Lett. 91, 233901 (2003)). / text

Thesis (M.S. in Computer Science)--Naval Postgraduate School, March 2005. / Thesis Advisor(s): Su Wen, Geoffrey Xie. Includes bibliographical references (p. 167-168). Also available online.

Thesis (Ph. D.)--University of Washington, 1999. / Vita. Includes bibliographical references (leaves 119-132).

Gray whales (Eschrichtius robustus), while engaged in underwater signalling, circumvent noise in the acoustical channel by the structure and timing of their calls. Data yielding this conclusion were collected during an acoustical study on gray whales and their habitats (1981-1984). Sonographic analyses of tape recordings were used to quantify the acoustical repertoire, the ambient noise characteristics of the area, and the relationship between the animals' calls and the environment. The acoustical responses of whales to artificially increased levels of noise were documented during playback experimentation in Mexico. Nine sound parameters were inspected and compared between control and experimental conditions: calling rates, call types, frequency range of signals (Hz), emphasized frequencies (Hz), received levels of sounds (dB re 1 μPa), call duration (sec), percentage of calls exhibiting frequency modulation, number of pulses per series, and repetition rates of signals. The observed surface behavior of gray whales in response to noise (i.e., dive durations, movements and abundance) was also investigated. Analyses yielded: a description of gray whale call types; a characterization of the acoustical habitats occupied by this species, including a list of sources contributing to the ambient noise and a profile of the propagation characteristics of the study area; a determination of the relationship between whale calls and their habitats; and the acoustical capabilities and strategies of whales in response to noise. The plasticity observed in the overall behavior of this whale is of adaptive significance when considering the dynamic nature of noise in the environment. Typically, the multiple strategies employed by the whales when faced with various noise situations enable them to minimize the detrimental effect that noise has on their underwater signalling. Gray whale responses varied with the sound source and may also differ relative to the geographical range and/or general behavior of the animal. It is concluded that ambient noise (both natural and man-made) has a profound effect on the behavior of this coastal species and that acoustical calling is modified to optimize signal transmission and reception. / Science, Faculty of / Zoology, Department of / Graduate

Summary: Acoustic differences were evaluated among three choral arrangements and two choral textures recorded at three microphone locations. A choir was recorded when singing two musical selections of different choral texture, one homophonic and one polyphonic. Both musical selections were sung in three choral arrangements: block sectional, sectional-in-columns, and mixed. Microphones were placed at the level of the choristers, the conductor, and the audience. The recordings at each location were analyzed using long-term average spectrum (LTAS). The LTAS from the mixed arrangement exhibited more signal amplitude than the other arrangements in the range of 1000-3500 Hz. When considering the musical selections, the chorus produced more signal amplitude in the region of 1800-2200 Hz for the homophonic selection. In addition, the LTAS produced by the choir for the homophonic selection varied across the microphone locations. As for the microphone location, the LTAS of the signal detected directly in front of the chorus had a greater slope than the other two locations. Thus, the acoustic signal near the choristers differed from the signals near the conductor and in the audience. Conductors may be using acoustic information from the region of the second and third formants when they decide how to arrange a choir for a particular musical selection.

No description available.

WHAT? The interconnectedness of acoustics and architecture is one that is too often overlooked. Many architects tend to focus solely on visual aesthetics, when in reality, it is the architect's job to create a space that is pleasing to all of the senses. Although all senses are important to the experience of a space, in most instances architects only have control over sight, sound, and touch. While architects usually make calculated decisions to improve the visual and touch experience, it seems that acoustics are an afterthought and rarely brought to attention unless there are special requests from the client or complaints from the user. WHY? The issues caused by poor acoustic considerations range from a space that is simply annoying to occupy, such as a desk fixed under the constant hum of an air vent, to rooms that are unusable for their intended purpose, such as a lecture hall with a long reverberation time making it impossible to distinguish syllables and understand the speaker. In the case of musical performances, the acoustical considerations of a design can completely alter the way sound travels from the performers to the audience. For example, a rock concert in a small room finished in marble would be unbearable, while a high school orchestra would be inaudible from the back of a large amphitheater. Therefore, it is important to design a space in which the architecture strengthens the performances that it was intended for. HOW? In this thesis I examine the balance of visual aesthetics and acoustical performance into a single building, the Shrine Hill Music Center. Located in Roanoke, Virginia, the Shrine Hill Music Center is imagined as a supplement to the surrounding educational buildings by housing a small performance hall, several practice rooms, and a recording studio to be enjoyed by students and members of the community. During my research I found myself asking questions such as; what architectural choices can be made that are both visually and audibly pleasing? What acoustical factors should be considered when designing a performance hall and how do these differ from those of a practice room or a recording studio? Is there an opportunity to tune a space just as one is able to tune an instrument? By the end I was not only left with a building that utilizes the architecture to enhance the acoustics, but also an abundance of acoustical knowledge that will benefit me in my future endeavors as a designer. / Master of Architecture / The interconnectedness of acoustics and architecture is one that is too often overlooked. Potential issues caused by poor acoustic considerations range from a space that is simply annoying to occupy, such as a desk fixed under the constant hum of an air vent, to rooms that are unusable for their intended purpose, such as a poorly treated lecture hall where it impossible to distinguish syllables and understand the speaker. In the case of musical performances, the acoustical considerations of a design can completely alter the way sound travels from the performers to the audience. Therefore, it is important to design a space in which the architecture strengthens the performances that it was intended for. In this thesis I examine the balance of visual aesthetics and acoustical performance into a single building, the Shrine Hill Music Center. I found myself asking questions such as; what architectural choices can be made that are both visually and audibly pleasing? What acoustical factors should be considered when designing a performance hall and how do these differ from those of a practice room or a recording studio? Is there an opportunity to tune a space just as one is able to tune an instrument? By the end I was not only left with a building that utilizes the architecture to enhance the acoustics, but also an abundance of acoustical knowledge that will benefit me in my future endeavors as a designer.

<p> The goal of this research is to investigate the feasibility and potential effectiveness of using vacuum-sealed, double-leaf partitions for applications in noise control. Substantial work has been done previously on double-leaf partitions where the acoustics of the inner chamber and mechanical vibrations of structural supports are passively and actively controlled. The work presented here is unique in that the proposed system aims to eliminate the need for active acoustic control of transmitted acoustic energy by removing all the air between the two panels of the double partition. Therefore, the only remaining energy paths would be along the boundary and at the points where there are intermediate structural supports connecting the two panels. The eventual goal of the research is to develop a high-loss double-leaf partition that simplifies active control by removing the need for control of the air cavity and channeling all the energy into discrete structural paths. </p><p> The work presented here is a first step towards the goal of designing a high-loss, actively-controlled double-leaf partition with an air-evacuated inner chamber. One experiment is conducted to investigate the effects of various levels of vacuum on the response of a double-leaf partition whose panels are mechanically coupled only at the boundary. Another experiment is conducted which investigates the effect of changing the stiffness of an intermediate support coupling the two panels of a double-leaf partition in which a vacuum has been applied to the inner cavity. The available equipment was able to maintain a 99% vacuum between the panels. Both experiments are accompanied by analytical models used to investigate the importance of various dynamic parameters. Results show that the vacuum-sealed system shows some potential for increased transmission loss, primarily by the changing the natural frequencies of the double-leaf partition.</p>

<p> Inharmonicity is a concept implicit in acoustic systems that explains the production of non-linear (non-integer) harmonics. While inharmonicity in and of itself is not always audible per se, its effects are no less than creating the basis for timbre and differential sound discrimination. In other words, inharmonic and non-linear signals are essential for human audition, yet they appear and disappear almost instantaneously. This paper attempts to elucidate the wide-reaching effects of inharmonicity and non-linear dynamic systems in a concrete sense by examining their relationships to the listening body and mind, as well as in an abstract sense in considering the theoretical implications of noise and non-linearity on the process of thought, potentiality, and subjective meaning-making. </p><p> The paper opens with several accounts related to foregrounding historical ideas about the relationship between sound and body, leading up to a contemporary understanding of sound in the sense of physics and acoustics. Therein, a modern account of inharmonicity and perception is given through current research in psychoacoustics, psychology, and dynamic systems. Finally, the tactic of &lsquo;creative listening&rsquo; is introduced following from a discussion of the relationships between noise and thought in 20^th- and 21^st century aesthetics and philosophy.</p>