Eventos Anais de eventos
COBEM 2023
27th International Congress of Mechanical Engineering
Validation of a time-domain model for acoustic impedance tube design
Submission Author:
Alexander Pasqual , SP
Co-Authors:
Alexander Pasqual, Thiago de Paula Sales
Presenter: Thiago de Paula Sales
doi://10.26678/ABCM.COBEM2023.COB2023-1573
Abstract
The two-microphone impedance tube method is widely used in acoustic testing to obtain the absorption curves of materials. It consists in mounting two microphones at the tube wall, and placing a loudspeaker and a test specimen at the tube ends. Hence, the absorption curve is obtained by driving the loudspeaker with a broadband signal and processing the microphone signals. Although there are ASTM and ISO standards related to the impedance tubes, their proper design requires an in-depth knowledge to decide on the loudspeaker features, excitation signal, tube dimensions, microphone positions, signal processing techniques, and signal-to-noise ratio limits. To assist the impedance tube designer, a time-domain model that simulates the pressure signals has been developed and described in a previous paper. This model applies the finite element method to the one-dimensional wave equation, coupled to the Thiele-Small model of the loudspeaker. In this work, we present a validation of the model through experiments in a commercial tube with three microphone positions, so that two different spacings between sensors could be tested. Also, white and pink noise excitation signals were considered, with different signal-to-noise ratios and three test specimens. A comparison of the experimental and numerical results showed that the model is able to simulate the acoustic behavior of impedance tubes. Thus, it can be used as a tool for designing impedance tubes and testing signal processing techniques.
Keywords
Impedance Tube, acoustic testing, acoustic signal processing, sound absorption, Finite Element Method
