Active Noise Control Systems for Windows Using Transparent Carbon Nanotube Actuators
Rajesh Rajamani, Professor, Mechanical Engineering
- Xun Yu, Former Associate Professor, UMD-Mechanical & Industrial Eng
Project Summary:For buildings located close to airports and highways, windows constitute the primary path through which noise enters the home. Double-glazed windows can block high-frequency noise but are ineffective at attenuating low frequencies. The use of a transparent thin-film acoustic transducer in a window can provide effective cancellation of low-frequency noise. For powering such an embedded noise-cancellation system, this research considers the harvesting and storage of solar energy. It utilizes transparent carbon nanotube films for an acoustic transducer that can generate sound in the 150?20 kHz frequency range, with a magnitude up to 100 dB. The use of the acoustic transducer as both an invisible speaker for auxiliary audio playback and for active noise cancellation is considered, and several challenges related to active noise cancellation in the window are addressed?including secondary path estimation and directional cancellation of noise so as to preserve auxiliary audio and internal sounds while preventing transmission of external noise into the building. Solar energy can be harvested at a low rate of power, while acoustic sound cancellation requires short durations of high power. The research, therefore, considers a supercapacitor-based energy storage system. A flexible thin-film fully solid state supercapacitor is developed that can be integrated into the window frame. The supercapacitor is a double-layer device that consists of thin-film carbon nanotube electrodes embedded in cotton paper substrates and a solid state polymer gel for the electrolyte. An energy density competitive with commercially available supercapacitors (which use liquid electrolyte) is achieved. In summary, the objective of this research is to develop several fundamental technologies that can contribute to a smart window. Since the component technologies being developed are fundamental, they have wider applications in domains beyond building windows. The thin-film supercapacitor could potentially be useful as a high energy and power density device that replaces batteries in hybrid cars.
- Start date: 09/2010
- Project Status: Completed
- Research Area: