Which type of discipline involves managing the amount of sound made in a tactical environment?

The correct choice is noise discipline. This concept is critical in a tactical environment because managing sound can significantly impact a unit's effectiveness and safety. Noise discipline refers to the practice of minimizing unnecessary noise to prevent detection by the enemy and maintain tactical surprise. In combat situations, even low sounds can compromise the element of surprise, make a position easily detectable, or alert the enemy to your movements or intentions.

For instance, maintaining noise discipline can involve actions like speaking in low tones, using hand signals instead of verbal commands, and carefully managing equipment and gear to avoid clanging or rustling. By enforcing strict noise discipline, forces can enhance their stealth, which is often essential for successful operations.

The other options, while they relate to different aspects of operational security and effectiveness, do not specifically address sound management in the same way noise discipline does. Light discipline involves controlling the use of lights to prevent visibility, litter discipline pertains to managing waste to minimize environmental and tactical footprints, and security discipline relates to maintaining tight control over valuable information and ensuring safety against potential threats.