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