What is the quietest gun in the world?

I'm curious, could you elaborate on what constitutes the quietest gun in the world? Are we talking about a specific type of ammunition or design that minimizes noise? Is there a certain brand or model that stands out as the most subdued among firearms? Are there any technological advancements or unique features that contribute to this low noise level? I'm eager to learn more about the factors that determine the quietness of a gun and which one truly reigns supreme in terms of minimal sound output.