Subwavelength-Sized Narrow-Band Anechoic Waveguide Terminations

We propose and demonstrate the use of a pair of detuned acoustic resonators to efficiently absorb narrow-band sound waves in a terminated waveguide. The suggested configuration is relatively simple and advantageous for usage at low frequencies, since the dimensions of the resonators are very small compared to the wavelength. We present a theoretical description based on lumped parameters to calculate the absorption coefficient, which agrees very well with experimental data. The experimental results verify that the anechoic (reflection approximately -38 dB) narrow-band (Delta f/f similar to 0.1) termination with deeply subwavelength (