Various frequencies have been tried: http://wdmc.org/1997/MilkingFrequency.pdf http://wdmc.org/1997/MilkingFrequency.pdf but technology has also advanced to th

Various frequencies have been tried: http://wdmc.org/1997/MilkingFrequency.pdf http://wdmc.org/1997/MilkingFrequency.pdf but technology has also advanced to the point where each cow can choose its own frequency: https://en.wikipedia.org/wiki/Automatic_milking#Advantages https://en.wikipedia.org/wiki/Automatic_milking#Advantages