By Lin Ying-yu 林穎佑
Taiwan’s domestically built Hai Kun (海鯤號) submarine was revealed to the public on Sept. 28, inspiring much discussion about everything from its appearance to its strategic applications. Notably, many observers have discussed its acoustic signature, which affects its survivability in potential combat situations.
A submarine’s acoustic signature, or sound profile, has important implications for its combat operations. The acoustic signature is the sound its machinery and propeller make during operation. Just like humans, each submarine has a unique “voice.” Each submarine’s acoustic signature is different, even for different submarines of the same class. Like human fingerprints, each sound profile is unique.
In underwater combat conditions, a vessel can only be detected by sonar, so underwater combat could be called acoustic warfare. Consequently, a submarine’s acoustic signature is an important way of identifying it.
Identifying someone’s voice requires two preconditions: First, one must have heard the person’s voice and have it stored in a memory “database.” Second, the person’s voice must have characteristics that can be used to identify it.
However, having data about a submarine’s profile is not enough to identify it during warfare in a marine environment. In such conditions, it can only be identified by combining that information with marine hydrographic data. In an underwater environment, which makes a vessel invisible, there are plenty of environmental variables that could have an effect on anti-submarine warfare, such as depth and temperature.
At the launch ceremony, the Ministry of Defense used a cover featuring Taiwan’s national emblem and colors to conceal the submarine’s bow-mounted sonar, torpedo tubes, stern propeller and side-scan sonars. The main reason for hiding them is that it is possible to estimate a submarine’s underwater capabilities based on the number, angle and configuration of its propeller blades, so the propeller blade configuration and related data are classified to protect the submarine from being detected by the enemy during combat operations. However, actual acoustic signature data can probably only be recorded during underwater operation tests, and there is not much chance that such a sound profile could have been obtained while the submarine was being built. This information must be kept secret as the Hai Kun enters its next phase of test operations.
Taiwan’s domestic submarine building program involves the hard work of a large number of people. Having had the good fortune of being invited to the launch event, a foreign reporter asked me whether I was surprised to see the submarine launched. However, the word “surprise” has a connotation of an unexpected or surprise attack. Rather than “surprising,” a better word to describe such an important moment for Taiwan’s naval and defense development would be “amazing.”
As well as establishing Taiwan’s undersea warfare power, the Hai Kun marks a big success for our national defense industry. Although we received a lot of assistance from abroad, this raises the question of how to apply project management and integrate technology and systems from various countries for the best possible performance in combat. Taiwan’s success in this regard would be an important indicator as to whether it can go on developing its self-reliance in national defense. Let us hope that, as well as adding the Hai Kun to its navy, Taiwan will also manage to create a fleet of silent submarines and reach its goal of revitalizing the military and expanding the nation’s sea power.
Lin Ying-yu is an assistant professor at Tamkang University’s Graduate Institute of International Affairs and Strategic Studies.
Translated by Julian Clegg
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