In Japan, about 250,000 transmission towers are located mainly in mountainous and coastal areas, with many over 50 years old and deteriorating due to salt and weather damage. Conventional inspections using visual checks or drones are large-scale, time-consuming, and costly, highlighting the need for a simpler method. This study proposes a technique using ultrasonic waves and multiple acoustic emission (AE) sensors to detect deterioration and assess remaining lifespan, demonstrating that signal attenuation and delay can reveal structural issues.