Sound Signals
- Sound signals are made by the ships whistle. They are either in the form of a short blast (approximately 1 second in duration) or a prolonged blast (approximately 4 to 6 seconds).
- Vessels maneuvering in the Great Lakes Basin are subject to Canadian modifications to these sound signals. More information regarding these modifications can be found here.
- Vessels nearing a bend or an area obscured by an intervening obstruction indicate their upcoming presence by way of one prolonged blast. Should this be heard by another vessel approaching the bend, they are to sound one prolonged blast in response.
- In situations where vessels may not be making alterations to their course sufficient to avoid a collision, 5 short blasts are meant to indicate this concern.
Maneuvering Sound Signals
Vessels in sight of one another can indicate maneuvering intentions by using the following sound signals:
| "I am altering course to starboard" | 1 short blast |
| "I am altering course to port" | 2 short blasts |
| "I am operating astern propulsion" | 3 short blasts |
| "I intend to overtake on your starboard side" | 2 prolonged blasts followed by 1 short blast |
| "I intend to overtake on your port side" | 2 prolonged blasts followed by 2 short blasts |
| "I agree to your intention to overtake" | 1 short blast, 1 prolonged blast, 1 short blast in that order |
Restricted Visibility Sound Signals
Vessels with visibility restricted by snow, fog, hail, sandstorm, etc are to make the following sound signals:
| A power-driven vessel making way through the water | One prolonged blast every 2 minutes |
| A power-driven vessel underway but stopped and making no way through the water | Two prolonged blasts every 2 minutes with about 1 second between blasts |
| A vessel not under command, a vessel restricted in her ability to manoeuvre, a vessel constrained by her draught, a sailing vessel, a vessel engaged in fishing and a vessel engaged in towing or pushing another vessel | One prolonged blast and then 2 short blasts with about 1 second between blasts |
| A vessel at anchor less than 100 meters | Ringing the forward bell rapidly for about 5 seconds every minute |
| A vessel at anchor more than 100 meters | 5 seconds ringing of the forward bell followed by 5 seconds sounding of the aft gong every minute |
| A vessel aground | Three distinct rings of the bell before and after it's respective anchor sound signals |
Note on Sound Signals
- While not described in the collision regulations, as a matter of common practice, vessels seeking to communicate in regards to potential course conflicts will often hail one another on VHF channel 16 (or, in the case of larger vessels, possibly the local VHF traffic channel). Upon receiving confirmation of the other vessel’s acknowledgment, they will switch to a working channel (in order to leave the emergency channel as free from chatter as possible) and proceed with discussions in regards to maneuvering intentions.