It exists today in steel pipe mills in the US, where the noise is such it is impossible to hear a voice -- even shouted -- from further than a foot away. Radios

It exists today in steel pipe mills in the US, where the noise is such it is impossible to hear a voice -- even shouted -- from further than a foot away. Radios are similarly useless due to background noise, so a catalog of hand gestures are used to communicate across the factory floor. It is almost impossible to communicate the wall of sound in one of these factories with words. On a side note, I would be curious to learn if this improvised sign language is consistent between mills, or regions.) In these same pipe mills I saw another curious method of communication which the employees referred to as "Mexican radio". (This was in south Texas where the preponderance of employees were Latino). The worker at one end of a 40-50 foot long pipe would put his ear to the end of the open pipe, and the worker at the other end would yell into the pipe. It worked surprisingly well (frankly better than yelling from a foot away into open air) but the safety officers weren't too keen on the idea as it put soft body parts (faces and ears) next to potentially razor-sharp pipe ends. Hand gestures were preferred and crossed any English/Spanish language barriers as well.