By early detection of single and multiple damaged locations and repairing or replacing defective elements, it is possible to prevent damage to other areas and structural elements. The use of thin-walled steel plates is on the rise in the building industry. Damage to these elements can progressively develop and spread to other elements, resulting in overall structural damage. This article focused on detecting single and multiple damaged locations in thin-walled steel plates. An effective feature extraction method based on wavelet analysis with a one-dimensional theoretical background to analyze two-dimensional modal signals was introduced. This method calculates the peak of disturbances and irregularities in various damaged locations and their surrounding areas. The suggested method was used to identify the center of single and multiple damaged areas with an error of less than 5 %. The numerical and experimental results confirmed the effectiveness and efficiency of the proposed method in detecting various damaged locations.