Abstract
Time Reversal (TR) is a signal processing technique that can be used to focus acoustic waves to a specific location in space, with most applications aiming to create an impulsive focus. This study instead aims to focus long-duration noise signals using TR. This thesis seeks to generate higher amplitude noise at a desired location over an existing method of broadcasting equalized noise. Additionally, this thesis explores various characteristics associated with focusing long duration noise using TR. The dependence of the focal amplitude on the duration of the focused signal is explored as well as the implications of using multiple sources when focusing noise. The focal amplitude decreases with longer duration and then levels off when the duration exceeds a few seconds. Coherent addition of focused noise is observed if all loudspeakers have coherent noise signals convolved with their reversed impulse responses. Lastly, focusing noise with a desired spectrum is explored. The use of audible sound for acoustic excitation is commonly employed to assess and monitor structural health, as well as to replicate the environmental conditions that a structure might experience in use. Achieving the required amplitude and specified spectral shape is essential to meet industry standards. The thesis seeks to understand the spatial dependence of focusing long-duration noise signals using TR to increase the spatial extent of the focus. Both one- and two-dimensional measurements are performed and analyzed using TR with noise, alongside traditional noise broadcasting without TR. The variables explored include the density of foci for a given length/area, the density of foci for varying length with a fixed number of foci, and the frequency content and bandwidth of the noise. A use case scenario is presented that utilizes a single-point focus with an upper frequency limit to maintain the desired spectral shape while achieving higher focusing amplitudes
Degree
MS
College and Department
Physics and Astronomy; Computational, Mathematical, and Physical Sciences
Rights
https://lib.byu.edu/about/copyright/
BYU ScholarsArchive Citation
Russell, Rylee Scott, "Time Reversal Delivery of Long Duration Noise to a Targeted Location: Achieving Higher Amplitude While Maintaining a Desired Spectral Shape and Maximizing the Spatial Extent" (2024). Theses and Dissertations. 11078.
https://scholarsarchive.byu.edu/etd/11078
Date Submitted
2024-12-18
Document Type
Thesis
Keywords
time reversal, long duration, steady state, spatial extent, multipoint
Language
english