Alarms on submarines of the United States Navy

Six standardized alarms are used on submarines of the United States Navy to alert the crew to situations that require immediate actions to be taken without waiting for specific orders. A higher priority alarm will silence an already-sounding lower one; in order of priority, they are:
# Collision Alarm
# Diving Alarm
# Missile Emergency Alarm
# Missile Jettison Alarm
# General Alarm
# Power Plant Casualty Alarm
The two missile alarms are used only on submarines that carry missiles.
A mnemonic aid for the order is the question "Can Dead Missile Men Get Pro-Pay?"
Collision/Flooding Alarm
The collision alarm is used to warn of imminent collision or actual flooding and is accompanied by a succinct statement of the emergency such as "flooding in engine room lower level" (if possible; flooding is deafeningly loud).
The alarm is a slowly rising and falling siren, rather like a stereotype American police car siren, which sounds continuously as long as the switch is held on.
The collision/flooding alarm handle is a red star shape.
Diving Alarm
The diving alarm is sounded twice to signal a dive and three times for surfacing, and is accompanied by either the announcement "dive, dive" or "surface, surface, surface."
The alarm is usually described as "ah-OOG-ah." On early submarines, it was an actual motor-driven vibratory horn (called a klaxon after the popular Klaxon Horn used on automobiles); later classes used electronic signal generators in the General Announcing System (1MC) that did not sound much like a klaxon but were variously described as "blats," "honks," or "cow farts." Motor-driven horns supplied by Benjamin Electric (Type H-9 horn) were installed in WW2 fleet submarines. Later motor-driven horns were mostly supplied by Federal Electric (later Federal Sign and Signal, changing finally to Federal Signal - Type H-8 horn) and are still found in certain applications today. Many modern submarines still have Klaxon diving alarms (mostly supplied by crew members or unofficial sources, usually not NAVSEA) paying homage to USN submarine tradition.
The diving alarm handle is a green square. Activation of the contact maker causes the alarm to sound until released.
Missile Emergency Alarm
The missile emergency alarm is used to warn of any emergency involving ballistic or cruise missiles, and is found on s and on s with VLS tubes.
The alarm is a fast jump tone, two high-pitched notes repeated several times a second. People asked to imitate the alarm often say "deedle-leedle-leedle" in a falsetto voice as rapidly as they can.
The missile emergency alarm is an orange crown shape.
Missile Jettison Alarm
The missile jettison alarm is used to warn of the imminent jettisoning (not launching) of a ballistic missile, and is currently found only on an Ohio-class submarine.
The alarm is a repeating rapidly rising tone, often compared to the "Red Alert" alarm from the original Star Trek series.
The missile jettison alarm on Ohio-class submarines does not have a handle like other submarine alarms. It is a key-activated alarm that only sounds upon energizing the missile jettison panel located in the Missile Control Center.
General Alarm
The general alarm is used to alert the crew to any emergency not covered by another alarm including all varieties of battle stations. It is accompanied by a succinct statement of the situation, such as "fire in Machinery Two" or "man battle stations strike."
The general alarm handle is a yellow oval. One turn of the handle causes the alarm to sound for a predetermined amount of time; fourteen gongs is a typical length.
Power Plant Casualty Alarm
The propulsion plant casualty alarm is used to warn of any emergency involving the engine room.
The alarm is a slow jump tone, two high-pitched notes repeated about twice a second, rather like a stereotype European police car siren. People asked to imitate the alarm often say "wee-ooo-wee-ooo" or "Dead-nuke, dead-nuke" in a falsetto voice.
The propulsion plant casualty alarm handle is a pink T shape.
Testing
All alarms are tested regularly. The crew is first warned that testing is beginning, then each alarm is sounded from every alarm location. Because the general quarters alarm lasts for several seconds, the collision alarm is sounded very briefly to override and cut it off. The many locations whence the collision alarm can be sounded were once traditionally tested from stern to bow, beginning with the engine room lower level aft location sounding the alarm as briefly as possible, then each subsequent location sounding the alarm for a slightly longer period of time. By the time the torpedo room sounds the alarm, it is held on for several complete cycles of the siren. Today, the sequence of collision alarm testing typically goes from top to bottom and forward to aft. In this sequence, the aforementioned engine room lower level sounds his alarm last.

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