Ray-tracing semiclassical (RTS) low frequency acoustic modeling validated for local and extended reaction boundaries

Abstract

The recently introduced acoustic ray-tracing semiclassical (RTS) method is validated for a set of practically relevant boundary conditions. RTS is a frequency domain geometrical method which directly reproduces the acoustic Green's function. As previously demonstrated for a rectangular room and weakly absorbing boundaries with a real and frequency-independent impedance, RTS is capable of modeling also the lowest modes of such a room, which makes it a useful method for low frequency sound field modeling in enclosures. In practice, rooms are furnished with diverse types of materials and acoustic elements, resulting in a frequency-dependent, phase-modifying absorption/reflection. In a realistic setting, we test the RTS method with two additional boundary conditions: a local reaction boundary simulating a resonating membrane absorber and an extended reaction boundary representing a porous layer backed by a rigid boundary described within the Delany-Bazley-Miki model, as well as a combination thereof. The RTS-modeled spatially dependent pressure response and octave band decay curves with the corresponding reverberation times are compared to those obtained by the finite element method.

Recording, Processing, and Reproduction of Vibrations Produced by Impact Noise Sources in Buildings

“…Since human sensitivity to vibrations is highest at frequencies below 100 Hz, as mentioned in [19], this frequency can also be considered the required upper operating frequency range of the accelerometer. As it turns out, this is not a challenging technical requirement, given the operating bandwidths of most commercial accelerometers.…”

“…Due to the insufficient sensitivity of the ADXL355-based design, a piezoelectric accelerometer was used in the next step, as such accelerometers are known to provide higher sensitivity. In addition, it was found in [19] that for impact noise in buildings, the vibrations in the vertical (z) direction in the frequency range below 100 Hz are at least 10 dB higher than those in the horizontal direction (x and y). Therefore, only the vibrations in the vertical direction of the sample need to be recorded, making the low-noise piezoelectric accelerometer a sensible choice.…”