|Basic (4 pt): Your drill and saw makes 65% less noise. Civilians and guards are less likely to hear your drill or saw and sound the alarm.|
|Ace (8 pt): Your drill and saw is silent. Civilians and guards have to see the drill or saw in order to sound the alarm.|
Non-upgraded drills, by default, have a sound radius of 25 meters. Guards or gangsters within this range will path towards the drill to investigate. If an object blocks the enemy's line of sight of the drill, this range is halved to a default distance of 12.5 meters. The basic version of this skill reduces the default sound radius to 9 meters, and 4.5 when the line of sight is obstructed.
Acing the skill reduces this radius to zero, meaning guards and civilians must spot the drill themselves to become alerted.
It is worth noting that this skill also affects the thermal lance used in some missions.
In loud heists, this skill is entirely useless, as sound radius is meaningless if the players have already been detected. On stealthy heists, this skill sees significantly more use (Firestarter Days 2 and 3, Nightclub, Big Oil, Bank Heist, Election Day, Shadow Raid, and Big Bank all benefit from this skill). However, there are some circumstances on quiet heists when loud drills are preferred over silent ones. One of the most common examples of this is the power box room on Firestarter Day 3. A loud drill can be started on this room on the roof of the bank to lure guards to a secluded area where they can be easily killed. If in doubt, it is best to consult with your team before silencing a potentially beneficial drill.
As the more practical drilling spots (security doors, safes, etc...) usually have more silent, faster and/or more efficient (but still quieter than drills nonetheless) methods of breaching like lockpicking, overriding, or simply by means of a keycard, acquiring this skill is only recommended if one were to rely mostly on drills to open up locked doors/safes during stealth, or are trying to unlock a higher tier in the Technician tree. However it's very useful if a titan safe must be opened silently since they can only be drilled.
- A silent drill/saw jamming still provides auditorial noise to the players, but not to NPC's. This is done due to gameplay reasons.