Micro-Grooved Elements - A Novel Solution for Noise Control

Non-linear Impedance of a New Sound Absorptive Fibreless Material Title

“…The samples differ for the porosity σ, the depth d of the channels, the width w of the channels, the length t of the channels, and the channel configuration. All the samples examined here have the width of the slots on the outlet layer g=4mm, which has been seen to be a preferable choice [11]. The Table I summarizes the ranges of variability of the previously mentioned parameters in the samples examined.…”

“…The MGEs have been first described in [11] and here a brief summary is reported. A MGE is typically composed of at least two overlying layers presenting macroscopic slots and a number of micro-grooves at least on one of the contact surfaces (see Fig.1a and Fig.…”

“…Since the experiments have been carried out by using different sound excitation levels, the Table 1 also includes the values of sound pressure level (SPL) measured within the 2-port test rig during the experiments. An accurate description of the test rig utilized in these experiments can be found in [11].…”

“…Once the reactive part of Z out has been measured, Z micro can be extracted from the measured ZMGE. The experimental procedure is detailed in [11].…”

“…Accordingly, the traditional MPEs are often considered too expensive for commercial applications. For this reason several fibreless solutions have been recently proposed, aiming to exploit the same physical principles while reducing the production costs [8], [9], [10], [11].…”