A second object of {HEAD ~ the present invention} is that, by providing an acoustic wave generation means for generating an anti phase sound in the vicinity of {TAIL ~ upper side part} of an exhaust outlet and providing a second pressure detector between the exhaust outlet and the acoustic wave generation means, a positive negative doublet sound source is constituted in a manner having the exhaust outlet as a positive sound source and the acoustic generation means as a negative sound source 
A second object of { HEAD ~ the present invention } is that , by providing an acoustic wave generation means for generating an anti phase sound in the vicinity of { TAIL ~ upper side part } of an exhaust outlet and providing a second pressure detector between the exhaust outlet and the acoustic wave generation means , a positive negative doublet sound source is constituted in a manner having the exhaust outlet as a positive sound source and the acoustic generation means as a negative sound source
OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH