The sound insulation effect of wooden keel is better than that of light steel keel, and it is much better to fill the keel with sound insulation cotton. Acoustic cotton is harmless. After careful study by the international cancer research institute composed of many first-class experts from eleven countries, it is confirmed that sound insulation cotton such as glass wool, rock wool and mineral wool will not pose a threat to people's health, and it was confirmed in 200 1, 10, 24. At present, soundproof cotton has been widely used in the world, so you can use it with confidence.
If you insist that you don't want to use it, you can also use the ordinary sea surface, but the sound insulation effect is worse. You can add a sound insulation board outside the keel to make up for it.