It was thought this might reduce propeller noise.

At 1305, the destroyer picked up a propeller noise and attacked with a second pattern of six depth charges.

The roar itself is not the only source of propeller noise.

And its sonar may have been disrupted by the propeller noise from boats above.

In the early morning, just off our French base, we heard the propeller noises of a foreign submarine.

It could double back and theoretically home in on the propeller noises of its own vessel.

The propeller noises of the destroyers sounded muffled, then clearer.

Then it switched on again, unaffected now from behind, could react to the propeller noises and head straight for its real target.

After half an hour the hydrophone operator heard faint propeller noises approaching.

At about 01:00 on 24 June 1944, Fish reported hearing some faint propeller noise in the area.