Experimental Comparison of Maximum Length Sequence (MLS) and Impact Hammer Methods to Evaluate Vibration Transfer Functions in Soil
The purpose of this paper is to test the validity of a pseudo binary sequence based method which is spectrally flat, and which is called MLS (for Maximum Length Sequences) to assess the differences in the level of vibration between different accelerometers, and evaluate key parameters that can be changed to improve the results. Before checking the validity of the MLS method, a description of the site where the test took place and a comparison of three different methods to setup accelerometers in soil are given. Measurements are also used to compute the improvement of signal to noise ratio as a function of the number of hits. Comparison between the impact hammer and MLS method is then analyzed. The main aspects of the signal processing used to analyze MLS and impact hammer signals are presented. Some information on the type of device used in the study and the primary characteristics of measured impulse responses are also presented. A comparison of mitigation at different distances between the MLS method (fixed parameters) and impact hammer method is then given. A parametric study is then performed on each MLS key parameter: MLS order, number of means, number of impulse responses analyzed, influence of background noise and linear behavior of the electrodynamic shaker. Finally, the variation of soil properties measured with the MLS and impact hammer methods over five days is given.
KeywordsLinear Feedback Shift Register Octave Band Impact Hammer Maximum Length Sequence Vibration Mitigation
Unable to display preview. Download preview PDF.
- International Standard Organisation, ISO 14837-1:2005: Mechanical vibration - Ground-borne noise and vibration arising from rail systems. Part 1: General guidance (2005)Google Scholar
- Houbrechts, J., Schevenels, M., Lombaert, G., Degrande, G., Rücker, W., Cuellar, V., Smekal, A.: Test procedures for determination of dynamic soil characteristics. RIVAS (Railway Induced Vibration Abatement Solutions Collaborative) project – Deliverable 1.1 (2011), http://www.rivas-project.eu/
- Madshus, C.: Test procedures for determination of dynamic soil characteristics, ISO committee TC108/SC2/WG8, ISO 14837 – 3.1 (project submitted to international survey) (2013)Google Scholar
- Kengni-Kengang, A.: Détermination métrologique des fonctions de transfert “infra-bâti” basé sur une source de vibration entretenue. Master degree thesis, Ecole Nationale Supérieure d’Ingénieurs du Mans (2012) (in French)Google Scholar
- Scilab 5.3.0 – Open and free software released under CECILL license and developed by the Scilab consortium - Digiteo, http://www.scilab.org
- Singleton Jr., H.L.: Vibration transfer mobility measurement using maximum length sequences. In: Proc. 150th Meeting of the Acoustical Society of America/NOISE-CON 2005, Minneapolis, Minnesota (2005)Google Scholar
- Coquel, G., Kengni-Kengang, A.: Comparison of impact hammer and maximum length sequence method to measure vibration transfer functions in soils. In: Proceedings of Internoise 2013, Noise Control for Quality of Life, Innsbruck, Austria, September 15-18 (2013)Google Scholar