Complement to standard method for measuring normal incidence sound transmission loss with three microphones

Abstract

Complement to standard E2611-09 of the American Society for Testing and Materials [Standard Test Method for Measurement of Normal Incidence Sound Transmission of Acoustical Materials Based on the Transfer Matrix Method (American Society for Testing and Materials, New York, 2009)] is proposed in order to measure normal incidence sound transmission loss of materials in a modified impedance tube using a three-microphone two-load or one-load method. The modified tube is a standard two-microphone impedance tube, where a third microphone is mounted on a movable hard termination. This method is conceptually identical to the four-microphone two-load or one-load method described in the standard; however, it requires fewer transfer functions and one microphone less. The method is validated on (1) symmetrical homogeneous and (2) non-symmetrical non-homogeneous specimens.

Acoustical properties of air-saturated porous material with periodically distributed dead-end pores

“…A three microphones method 12 is used to get the virtual FEM measurements. In the FEM model on COMSOL, parabolic tetrahedral elements were used to mesh the different domains of the tube and an effective fluid of density and bulk modulus given by the JCA model 9,10 fills the pores.…”

Prediction of the acoustic behavior of a parallel assembly of hollow cylinders

“…The measurements are done according to the three-microphone method [14] and standard ASTM E2611-09 [15]. The acoustical tube is a 44.4 mm diameter circular tube, and its cut-off frequency is 4100 Hz.…”

A semi-phenomenological model to predict the acoustic behavior of fully and partially reticulated polyurethane foams

“…24 The two characteristic lengths (K,K 0 ) and the thermal permeability k 0 0 are determined using the indirect characterization method proposed by Panneton and Olny 25,26 based on the JCA model modified by Lafarge 27 (also called JCAL). This indirect method requires the measurement of the equivalent dynamic bulk modulus K eq and equivalent dynamic density q eq of the tested material performed here using the 3-microphone impedance tube method proposed by Salissou et al 28 The Lafarge et al model 27 is used in the characterization method to model the equivalent dynamic bulk modulus K eq because it was shown elsewhere to match more closely its low frequency behaviour. 2 This determination of the parameter k 0 0 is mainly used here to lower the error in the determination of the thermal characteristic length K 0 .…”