"Chinese Type 039G Song-class No. 314 naval submarine docks at the Ngong Shuen Chau naval base in Hong Kong."
1. Modern teardrop hull shape
2. Engine mounted on shock absorbers
3. Anechoic tiles. "Internet-source photos of Type 039s under construction also show Chinese mastery of advanced multi-layer rubber/polymer hull coatings that greatly reduce hull-radiated noise while also limiting the effectiveness of active-sonar detection."
4. "Large asymmetrical seven-bladed skewed propeller" to reduce cavitation
5. Diesel-electric engine design "insulates the noisy diesel engines from the pressure hull, making the submarine quieter." A diesel-electric submarine can "operate virtually silently while on battery power."
6. Tight tolerances during manufacturing by using advanced Chinese 7-axis machine tools. "It probably should be noted that blade noise among Soviet/Russian submarine types dropped dramatically after Japanese electronics company Toshiba and Norwegian company Kongsberg sold advanced milling machinery and control equipment to the USSR in the mid 1980s."
References:
a.
Type 039 submarine - Wikipedia, the free encyclopedia [1,2,3]
b.
International Assessment and Strategy Center > Research > Top Ten Chinese Military Modernization Developments (see section VIII) [3; second sentence]
c.
Chinese Navy [3,4]
d.
http://www.globalsecurity.org/military/systems/ship/systems/propellers-supercavitating.htm [4; reduce cavitation]
e.
Submarine - Wikipedia, the free encyclopedia [5; first sentence]
f.
http://www.hsdl.org/?view&did=445936 (p. 29) [5; second sentence]
g.
HarpGamer > Tactics 101: Anti-Submarine Warfare - Part 3 (see
Target Identification) [6; second sentence]
----------
From my April 14, 2011 post:
China's CKX5680 Digitally Controlled 7-axis Contour Milling Machine
The Wuhan Heavy Industry Corp. just made a breakthrough in an 863 Project. This is the CKX5680 Digitally Controlled 7-axis Contour Milling machine. This is significant as it is specialised in building ship propellers, like this one, for aircraft carriers and submarines. It is much more precise than 5-axis machines.
[Note: Thank you to "pugachev_diver" for the post.]
----------
Type 039 Song-class submarine with asymmetric seven-bladed skewed propeller to reduce cavitation