A system 1, wherein the system comprises {HEAD ~ a phase locked loop} for measuring the amplitude of {TAIL ~ a photoacoustic signal} 
A system 1 , wherein the system comprises { HEAD ~ a phase locked loop } for measuring the amplitude of { TAIL ~ a photoacoustic signal }
OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL