Experimental research on hollowing detection in concrete walls based on acoustic signal feature analysis

Concrete wall hollowing is a common defect affecting structural safety and durability, and its accurate identification is of great significance for ensuring the quality of construction projects. To achieve efficient and non-destructive detection of hollowing defects, this paper proposes a method for identifying the state of concrete wall hollowing using the characteristics of knock sound signals based on the principle of acoustic response. The study first collects acoustic signal data from hollowing and non-hollowing areas through standardized knocking experiments, and conducts systematic time-domain and frequency-domain feature analysis. By comparing signal waveform and spectral characteristics, the study explores the differences in acoustic response between hollowing and non-hollowing areas. The research results provide a reliable parameter basis for acoustic detection of concrete structures and verify the feasibility and effectiveness of the hollowing identification approach based on acoustic signal characteristics. This research method has the advantages of simplicity, low cost, and strong applicability, and can provide new technical support and application references for non-destructive testing and intelligent health monitoring of building structures. The results show that under the experimental conditions of this study, the dominant frequencies of hollow areas are mainly distributed in the range of 1650-1750 Hz, while those of non-hollow areas are concentrated within 1300-1500 Hz. The absolute values of peak amplitudes of hollow areas generally fall between 40-50 mV, whereas those of intact regions range from 10-20 mV, which provides quantitative reference criteria for hollow defect detection in practical engineering.