This work presents an experimental characterization of three types of ground commonly found in urban centers regarding their absorption properties with respect to sound propagation: asphalt, grassland and soil. A brief theoretical background is presented, and the experimental procedure is discussed in detail. With basis on experimental results, it is concluded that grassland ground is mostly absorbent for all tested frequencies, whereas asphalt and soil are reflexive for low frequencies and absorbent for high ones.

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Sound insulation can be difficult to forecast. In most cases it is necessary to take certain precautions in order to avoid degradation in the acoustical performance of walls. Knowing that sound transmission through walls depends on mass per unit area, bending stiffness, damping, mounting conditions, frequencies, etc., the sound transmission can be explained theoretically by several hypotheses. Even though sound transmission has been investigated for more than 100 years, there still remain a lot of issues to be solved. The purpose of this work is to present a discussion regarding the main analytical models used in sound reduction by simple walls, to help the engineer in noise control projects for industry or homes. Several model cases were analyzed by numerical estimation, and the best results were selected to perform experimental comparisons. Some comparative graphics are presented to compare numerical and experimental results. [Work supported by CAPES.] (To be presented in Portuguese.)