Abstract: The invention relates to a method for estimating the contents of particulate solids in a solid container, comprising the steps of: a) providing a percussion device; b) hitting the surface of the container on it outside with said percussion device at predetermined distances along the height of the container; c) recording the sound created by said percussion; d) identifying the sound generated by each recorded percussion at the percussion time within a plurality of percussions; e) applying a analysis algorithm to a digital representation of the sounds identified in d above; and e) determining the heights of the container that is filled with particulate material by locating the height at which the value resulting from the analysis of each percussion changes from a high to lower value, wherein a higher value indicates an empty portion of the container, and a lower value indicates a filled portion of the container.