It is funny that you guys crows about China's indigenous jet engine, which
STIL have problems, but make every nonsensical attempts to denigrate the JPNese effort.
If you want long range and long duration for a cargo aircraft, a multi-engine platform is necessary. If the JPNese felt that for their maritime patrol purposes, four engines are better than two, then they will design a four engines platform. If four F7s get the P-1 off the ground inside a certain runway distance, up to a designated mission altitude, and cruise for a certain amount of time, the engine is a good design.
Your comment about the T/W ratio is absurd because in order to have that ratio, there must be a weight, and if we install the F7 into another and lighter aircraft, there would be a higher ratio, thereby it is ridiculous to criticize the F7 about its T/W ratio when it is used in the P-1 and that combination accomplished its mission.
Hello ? Do you have any experience in aircraft design ? Are you OK ?
Riiiight...
There is no denying the fact that the turboprop is noisier than the turbofan. But the noise in reference here is for the sub, as in a sub can hear the aircraft's engine noise. This is well known since WW II submarine warfare. The Tu-95 with its counter rotating props are so loud that some US pilots who have escorted that aircraft reported they could hear the -95's engine noise thru their helmets and headsets. The Tu-95 is reputedly the world's noisiest propeller driven aircraft.
You think I make this shit up ?
http://www.bbc.com/future/story/20150225-the-worlds-noisiest-spyplane
So in a manner of speaking, the turboprop's noise does affects submarine detection -- the sub can hear it and know someone is up there.