Chinese towns are generally quite clean, but a lot of street cleaning takes place because the concept of not littering does not exist in most areas. The rule is: “throw your ice cream wrapper on the ground somebody else will clean up”. In restaurants this concept extends to throwing bones and paper napkins onto the floor. Of course the local street dogs and cats help with the cleaning up, often entering the restaurant and encouraging patrons to drop more meaty scraps on the floor.
However, as we have moved to desert areas where there is a lot of dust in the air, more mechanized methods of street clean have become prevalent. I assume this is because the required army of street cleaners would otherwise be too large. Here in Hami, this is combined with a tendency to take catchy tunes that we westerners associate with certain occasions, and re-use them in completely unrelated contexts. For an example, see video below.
This street cleaner plays a well known tune to warn of its presence