Continuous noise in pipes as water is running is caused by something loose in the path of water flow that is allowed to move around.
It is most commonly caused by a loose washer, but could be dirt in the pipe or similar.
You can use the stop vavle on the toilet to shut that off. If the noise continuses when other water is flowing then the most likely problem is the main shutoff.
Other which the problem could be in the toilet fill valve or the stop valve.
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