Sound absorption by textile resonators

Since the first usage of absorbing structures to modify architectural acoustics the dampening of low frequencies has proven to be a difficult issue. Due to the rise of the population and concentration of said population in urban areas, also known as urban densification, the noise level has risen over the last years. A long-term exposure to noise can lead to serious health problems such as high blood pressure and sleep deprivation. The omnipresent sound in urban areas has a direct impact on the personal well-being. Currently used broadband absorbers work well in a frequency range from 300 Hz to 5 kHz. The dampening of frequencies below 300 Hz, especially below 200 Hz, requires large voluminas due to the wavelength and the absorbing mechanism. To achieve absorption of low frequencies a textile resonator with multiple absorbing mechanisms is proposed. The conversion of energy from the acoustic pressure field in mechanical oscillations as well as heat provides the possibility for efficient absorbers without large voluminas. Compared to common membrane resonators, which similar to Helmholtz resonators use a closed cavity behind the membrane, the textile resonators do not need a closed cavity to generate friction and visco-thermal losses.