Acoustic trauma is entirely preventable and totally untreatable. Noise damage is most frequent in industrial societies and is caused by a variety of sources. Radios with earphones and loud music at rock concerts are thought to cause damage. Manufacturing processes are know to damage hearing. Aircraft and trains are knowing to cause hearing loss. In rural settings, simple sugar-cane crushers are very noisy. Men who work with such machines, tinplate workers, and those who hammer out old oil drums for roofs and fences are subject to a level of noise which causes progressive high-frequency hearing loss and eventually deafness for the speech frequencies.