Laser Doppler Vibrometry Based Remote Sensing for Active Noise Control

Demands for active noise control/cancellation (ANC) to provide a quiet environment have grown significantly over the past few decades. Notably, many ANC headphones and earphones have emerged and gained much success in the market due to their excellent performance and robustness. There are also other ANC applications, such as ANC headrests and ANC windows. However, developments for such applications have been slow. Particularly, the physical presence and the number of required sensors, typically condenser microphones, severely limit the performance of many ANC applications. Laser Doppler vibrometry, which works on the principle of optical interferometry, has been widely used in to measure vibrations in many vibro-acoustic applications. Yet, the developed instrument, laser Doppler vibrometer (LDV), has little been studied in the published literature in the context of sound/noise measurement and control. This thesis, therefore, investigates and develops LDV-based remote acoustic sensing techniques for ANC applications, particularly ANC headrests and windows. The first part of the thesis studies how to use an LDV together with customised retro-reflective membranes to acquire acoustic information at discrete locations from a remotely positioned LDV. Then, such a configuration is used for remote error sensing in an ANC headrest scenario. The experimental results show significant improvements over the state-of-the-art systems. The reference signals are also investigated in ANC systems. Results show that a non-minimum-phase secondary path may require reference microphones to be installed at a considerable distance away from the secondary sources to have an adequate control performance, especially for the low frequencies. This is impractical in many applications. Remote acoustic sensing can also be applied for the reference signal. The second part of the thesis is concerned with measuring and controlling noise over a large area, e.g., at a window. Instead of measuring with a microphone array, refracto-vibrometry can serve as an alternative method. The major advantage of this technique is that it enables sound pressure measurement at all points of interest without disturbing the sound field and with high spatial resolution. Such a technique is preferable for noise control at windows and openings where ventilation and access are prioritised over the introduction of physical sensors. The sound field at an enclosure opening is measured in the experiment and used for the error signals for ANC. Results show that using refracto-vibrometry to measure a sound field can give a much finer resolution than using a microphone array for an ANC system.

Author dc:creator

• Xiao, Tong

Statement dc:rights

• info:eu-repo/semantics/embargoedAccess
• The author owns the copyright in this thesis including all reproduction and reuse rights for the work. The work may not be altered without the permission of the copyright owner. Attribution is essential when quoting or paraphrasing from this thesis.
• © 2022 Tong Xiao
• au.edu.uts.lib/ppc

Language dc:language.iso

en_US

Handle dc:identifier.uri

http://hdl.handle.net/10453/167122

OAI identifier oai:identifier

oai:opus.lib.uts.edu.au:10453/167122