Weird underwater noise, Corran Narrows

[mm5aho]

ON the return from a 2 week "round Scotland" sail, we moored on last Friday night near Corran Narrows. There are 5 free moorings listed as being provided by fish farmers for visitors, and we used one. I noted a small motorboat only other boat nearby was a yacht anchored between where we were and the ferry slip.
Soon after we settled down to eat, we noted a weird noise carrying through the hull.it was quite irregular, and sounded something between mechanical and electronic. I have a recording, but am unsure of how to upload it.

Can only assume this is some part of the nearby fish farm, but it sounded more like birds twittering, then the sound a playing CD makes when it gets stuck - a sort of stuttering machinegun effect.

Any ideas what this is?

[Silkie]

Seal scarer?

[wully]

Seal scarer?

mm5alo scarer?

[mm5aho]

It wasn't a scary noise, just puzzling.
I can sleep through anything other than unwelcome noises, which I seem to be able to detect. (like anchor dragging, alarm clock, phone ringing).
With 2 other snorers aboard, the noise didn't keep me awake after I'd accepted it as not a threat. But my light sleeping wife and son found it irritated their sleep.

Seal scarer is a possibility.

One other time I heard weird noises was in Lamlash, which I've since reconciled to be crustaceans of the lobster / prawn type - a tail clicking noise.
Another was on the old moorings in Ardminish Bay, Gigha, chain rattle of the mooring.

[marisca]

If you had had a keek at the fish farm, each compound had a rotating arm, one of which squeeked. What the purpose was I dinnae ken.

[mm5aho]

The rotating arm in the centre of round fish farm cages is the feeder mechanism. From some central point, feedstuff (made just down the road from where I live, and detectable with olefactory disgust in easterlies) is blown pneumatically through plastic pipes to each cage where an offset elbow on a bearing sprays it out into the water in a circular pattern. The shape of the curve of the pipe causes it to spin when air/feed mix is squirted down that tube. Each cage gets some in rotation.

The underwater noise didn't coincide with the feed system (timing wise), so I don't think it was that, but might have been part of the central system, though in that particular system the central feed distributor is on-shore. In most cases its on a barge floating alongside the cages.

[Booby Trapper]

Are there tidal turbines there?

[marisca]

I reckon the rotation and the noise were in synch. I spent the night on a fishfarm mooring and then sailed north past the cages. Noise louder in the boat than the air but I was sure I had identified the source.

[mm5aho]

If I could find a way to post the audio I would be able to demonstrate it. Its repetitive, 2 distinct noise types but irregular spacing.

[mm5aho]

phpBB [audio]

Hopefully this will play the recording we made of the noise.
This was done on a phone, just recoding what we could hear inside the cabin.
Its therefore not very loud, you might need to wind your volume up?

[BlowingOldBoots]

Have you checked for any signs of alien visitations?

Seriously, that is a strange noise, the eeeewwwwiiiii sounds like a weird RF interference. Maybe a submarine was transmitting in code and your boat was picking it up, apparently they use odd frequencies.

[marisca]

Yup, same noise, definitely water-borne but just about audible on deck. I still reckon it was squeaky fish feeders 'cos the air-borne noise got louder as we passed the fish farm cages going north. Aliens or submarines are much more exciting, though.

[mm5aho]

That noise was going when we arrived, was still going the several times I woke up during the night, and still going when we left.
The few thumps heard in the recording are not part of that, they're the mooring buoy touching the bow or similar.
There seemed no pattern to the two different phrases of the noise.

I agree that its most likely to be fish farm feeder equipment, but I can't think what. We didn't go closer to the cages to find out.

One of life's continuing mysteries

[Pilgrim]

Unfortunately I can't hear your recording but we also heard an odd noise when moored at Kingairloch Loch a Choire just south of your anchorage this summer on our way home from Shetland via the Caledonian canal. It started at 10pm and appeared cyclical, it was odd enough to even disturb Mark's sleep and we both found ourselves getting up mid way through the night to peer into the bilges to try to find the source. Eventually we decided it had to be from the fish farm approximately 1nm away. It appeared much more infrequent during the next day or perhaps it was drowned out by our two children's noise. As far as I can tell it sounded very similar to the noise you heard- perhaps only Rival owners on the way home from the north can hear it?! Liz

[marisca]

My crew often report being woken at night by a strange rythmic rasping noise. Strange thing is I never hear it and they claim it stops when I awake. Could this be the same noise?