<p>Bolt connections are integral to civil infrastructure and mechanical assemblies, where bolt loosening poses risks of structural instability and safety issues, potentially causing injuries and financial losses. Monitoring the loosening of bolts can mitigate accident risks, enhance safety, and prevent disasters. Consequently, understanding and identifying bolt connection integrity is a critical aspect of structural research. This study introduces a quantitative approach for detecting bolt loosening through controlled small ball impacts. By adjusting the bolt torque within a defined range to simulate varying levels of tightness or looseness, a small ball is released from a consistent height to strike the bolt. PZT sensors, mounted on the back of the flange, capture the impact signals, with multiple measurements taken across bolts. Both experimental and simulation results demonstrate that under specified conditions, the acquired vibration energy increases progressively with bolt torque enhancement. The proposed ball impact and energy processing methodology achieves successful and precise detection of bolt loosening states. This technique is low implementation cost, significantly reduced wave attenuation compared to ultrasonic methods, along with extended propagation distance and broader coverage range, compact spatial requirements, and simplified detection apparatus. This method can be used as automated detection in specific structural configurations.</p>