Piezoelectric Sensors in Theaters and Concert Halls Can Protect Hearing While Harvesting Energy
By lining a venue with piezoelectric sensors, excess noise can be diminished — and converted to useful electricity in the process.
Researchers from India's Ramaiah Institute of Technology have suggested a way to solve two problems at a single stroke, by absorbing excess and potentially harmful sound energy in theaters and concert venues and turning them into useful electrical energy.
"According to the Centers for Disease Control and Prevention, an estimated 12.5 percent of children and adolescents aged 6-19 years and 17 percent of adults aged 20-69 years have suffered permanent damage to their hearing from excessive exposure to noise," says Rajendra Prasad P, corresponding author on the team's paper. "Noise above 70 decibels for a prolonged period of time may start to damage our hearing. We need systems that can mitigate really big sounds."
Ignoring personal protective equipment, like earplugs, which require an individual to arrive fully prepared for excessive noise, the typical approach to capturing the unwanted sound waves is simple enough: soft fabrics and padded foam on the walls and ceiling, which softens echoes and prevents the sound from bouncing back. The research team, though, has a different approach, and one which turns the sound energy into something useful instead: electricity.
"Sound energy absorbed using piezoelectric sensors is processed by our system to convert it into electrical energy. Based on the pattern of energy generation, the output of the system is switched between battery and direct harnessed output," Prasad explains. "The surprising fact is the output of the design is maximum around certain frequencies that align with the frequency and intensity of the sound used in theaters or auditoriums. Our design reduces the vibration of sound each time it reflects from the piezoelectric material and reduces the overall sound intensity of the enclosed space."
The team's prototypes, tuned using computer simulation, use quartz-based piezoelectric sensors on the walls, floors, and ceiling, absorbing the energy of incoming sound waves and outputting a usable 12V supply between 70 and 90dB — with some venues hitting peaks of 120dB, the team notes. As well as reducing the reflected noise, and thus protecting listeners' hearing, the harvested energy can be used elsewhere — charging a supercapacitor which could power safety lighting in darkened theaters, the researchers suggest.
The idea of combining personal and environmental protection through the novel application of technology is at the heart of the Hackster Impact Summit 2023, which has its last day today and covers topics ranging from the development of smarter and better-connected cities to the sustainable development of societies — and includes Community Spotlight sessions highlighting projects created by the Hackster community.
The team's research has been published in the journal Physics of Fluids under open-access terms.