Measurement kit for Transmission Loss testing
4Mics_MAA kit permits the measurement of the normal incidence Transmission Loss and the complex reflection and transmission coefficients by using the transfer matrix approach by using a four microphones technique in the frequency range between 50 Hz e 4300 Hz
Parameters
- Complex reflection and transmission coefficients;
- Power reflection, Transmission and Absorption coefficients;
- Transmission Loss.
Technical specifications
Tube diameter: 45mm.
Measurement chain:
- 4 (¼” ) microphones and preamplifiers;
- 4 channels signal conditioner;
- Power Amplifier for output signal;
- National Instruments device or Audio sound card. The sond card has to work in full duplex
- Software developed in Labview®.
Frequency range: 50-4300 Hz.
Excitation signal: Exponential sine sweep.
Post-processing procedures: Power and cross spectral density functions of impulse responses obtained by using convolution of exponential sine sweep.
The transfer matrix approach is used for calculating the acoustical parameters.
Applications
The kit can be used for measuring the transmission loss of homogeneous and layered systems used in automotive applications. Moreover the measurement set-up permits the complete evaluation of performances of mufflers and silencers without mean flow in terms of reflected, absorbed and transmitted waves.From reflected and transmitted wave components it is possible to determine the complex reflection and transmission coefficients (amplitude and phase) wich could be used in a multi-port circuit for calculating performance of an entire exhaust system (including properties of engine and flow as well).
References
F. Pompoli, P. Bonfiglio, Tecniche avanzate di caratterizzazione fisico-acustica di materiali porosi, ATTI 35° Convegno AIA, Milano 11-13 Giugno 2008.
Download pdf
P. Bonfiglio, F. Pompoli, Comparison of different inversion techniques for determining physical parameters of porous media, Proceedings of ICA 2007, Madrid September 2-7 2007.
Download pdf
 |
