{TAIL ~ Two or more vibration generators} may introduce vibrations with different frequencies into the chemical bath liquid and at {HEAD ~ different angles} 
{ TAIL ~ Two or more vibration generators } may introduce vibrations with different frequencies into the chemical bath liquid and at { HEAD ~ different angles }
TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD