'Snap crakle and Pop' noise from under hull?

[tcm]

Re: \'Snap crackle and Pop\' noise from under hull?

it's between the two. Yakking away with a mate you wouldn't hear it. On your own, you do hear it and no real need for shallow breathing. Rice krispie noise pretty much describes nature and volume.

 

[tcm]

\"the clown who advised me\"

can't let this go.

To all (esp newbie posters) - advice on this forum carries NO guarantee whatsoever. You might ask a question and total utter tripe is given in response. YOU have to decide how to approach any task and there is no onus on anyone to answer, nor to answer correctly, not even to give a ridiculous jokey answer such as drilling an even numbers of holes in the boat to ensure that for each hole that lets water in there's another to let it out.

In this specif example, someone has (possibly) incorrectly advised someone to "polish" a stainles steel pushpit with a stainless steel panscrub, which is a v agressive item. No, not me that gave the advice but it matters not a jot. S/S would have to be very far gone to use that. In any event, it might have been a common sense idea to try a little area first, hm? Nope, panscrub in hand our courageous poster belts in and does the whole lot with nary a second thought on looking at the bits he's just done with the net result is that the whole thing ends up dull. Who's the clown?

 

[William_H]

Re: \'Snap crakle and Pop\' noise from under hull?

Certainly in the Swan Rive they are Snapper prawns making the noise. They are about 2cms long with one very pronounced claw and one tiny one. They live in the sand not usually on a hull and they stun their tiny prey with the shock wave of snapping their nipper together. You can catch them occasionally unnder rocks etc. However......................
I supect that the nature of seawater is to conduct the higher frequencies better than the low so that possibly many other source noises could end up sounding similar through a hull. This might give the opening for other answers. olewill

 

[Swagman]

Re: \'Snap crakle and Pop\' noise from under hull?

Hi Olewill,

I was lucky enough to live in WA for 20 years and I've also listened to the same / similar noises coming from below reef ledges on various bays at Rottnest - both when lying below decks on ali and GRP yachts - and when snorkeling off the reefs.

When diving, the noise always got more pronounced (not more rapid or anything - simply louder) the closer one got to each dark hole. So I don't think it was coming from any other locations - and certainly not from a mechanical source.

If anyone scuba dives or even snorkels a lot, they'll know exactly what engines and props sound like underwater. It's nothing like this this kind of 'snap crackle pop' which I think is replicated quite well at Brendans sound bite.

So to say it all again (and hopefully one last time)....
if its nothing to do with differing hull contruction.....
and on Rottnest it can't be anything to do with spring water.....
and as I've sat alongside fishes watching them eat - and they're really quiet and well mannered.......
and the crayfish and crawlies in WA don't have invisible outboards bolted on.........
and the sound bite of Brendans labelled as snapping shrimps matches the sounds I've heard......

then at least for me, this issue is settled.

JOHN

 

[nealeb]

Re: \'Snap crakle and Pop\' noise from under hull?

No idea exactly what causes it, but it had me out of my berth trying to track it down last weekend, anchored in flat water just behind Pilsey Is in Thorney Channel, Chichester Harbour. It sounded most like burning paper - that same kind of irregular, almost clicking/rustling, sound, and quite unlike any prop noise that I have heard (and that worried the whatsits out of me the first time I heard it, caused by a ship quite a long way off). First time I had heard it, and had me chasing around looking for electrical sparks, smell of burning, etc, but eventually decided it was wildlife doing me a favour by removing some of the weed off the hull. It was a very quiet night, and none of the boats that had motored past earlier had caused anything like the same noise. Volume? I was listening to the radio at a lowish volume and could hear it over that.

 

[tcm]

Brendan\'s shrimps

In the interests of chiming in and helping a thread along (on PBO! who wd've believed it?)

1 I am quite prepared to believe that it's snappy shrimps but there must be quite few around our boat. I am amazed that the french don't fryem up and serve them with marinade as a nice starter? I bet they would. Indeed this wd be my main or even only argument against the shrimp theory - the lack of local snappy shrimp maison entrée at in ANY french restaurant.

2 Brendan was a bit out of order and he has def hauled others in for less. I spect he must've gone ahead with buying the BMW X5 or even some tankish getoutamyway motor like a Toerag or perhaps a LWB Mercedes-Panzer ML Ardennes Invasion Special.

Nonetheless, i can understand that he put a bit of work into finding an answer right inside his area of expertise - and then somebody who didn't read his response chimed in half an hour later with another pronouncement, since partially withdrawn. Mind you, I've been much worse. So er, he probably got the bad manners from me. Hm. Sorry everyone.

 

[KevB]

It\'s not shrimp and it\'s not prop noise.

My penneth's worth says it male fish vibrating their swim bladders either to attract a mate or as a warning to rivals.

On the other hand it could just be the current moving the sea bed causing all the shells and stones to "click" together, with the sound travelling through the water and being amplified by the boats hull.

Take your pick of the two cause either is more laudable than all the other answers here. /forums/images/graemlins/grin.gif

 

[BrendanS]

Thread drift

Just speccing up a Touareg V10, and found an online dealer who claims to be able to deliver faster and cheaper than VW dealers, so very tempted

 

[AuntyRinum]

Re: Brendan\'s shrimps

"and then somebody who didn't read his response chimed in half an hour later with another pronouncement, since partially withdrawn"

tcm, I haven't partially withdrawn what I said and I did read his response. I didn't make a pronouncement either, just chose to put forward an alternative view, and there will be many reading this forum who will know exactly what I was talking about. Trust that's alright with you and in the spirit of this forum.
"an answer", yes, but not neccesarily the answer. Your postings on this seem to have been perfectly rational and polite which is what I would hope for on here.
Re Courageous' remarks, I am careful never to present myself as an expert on anything. I always remember the old adage that an ex is a has been and a spurt is a drip under pressure.
I don't claim that I have the answer (as so many do) but an alternative suggestion. There have been several alternative suggestions on here such as fish bladders and I don't see them attracting such vitriol as the response to my first post.

 

[tcm]

Re: Brendan\'s shrimps

fair enuf brettH. I only said you partially withdrew since you didn't press your case as hard when challenged. I withdraw the notion that er you withdrew.

 

[tcm]

Brendan\'s oberwagen

hm, but you get less warranty doncha with "genuine" uk importy special. And they often lie about it and when it's in your name it says "number of previous owners - 1" or at least check this doesn't happen.

Anyway, i reckon an Ardennes Special is an excellent idea. German offroad cars don't do this yet but it is *bound* to happen eventually, with options for making it a halftrack and so on. Oh, it might sound bad taste at the moment but for a while nobody wd dream of buying german car, now it's fine , and as far as being ghoulish is concerned, *exactlty* the same sort of thing happened in the sixties with the Daimler Conquest (so called cos it cost £1066 new) but which actually commemorates a battle which killed thousands and heralded 20+ years of violence killing loads of brits and celts.

Praps ask for a Hitler pack and see what he says. Or ask for a winter pack and see if can be uopgraded to a "winter 1941" pack. Not everything is on the brochure you know.

 

[BrendanS]

Re: Brendan\'s oberwagen

Ah, but not import. They source from UK dealers, and you are first registered owner. All above board and kosher and came recommended by peeps who have gone via this route.
Like the idea of a halftrack tho, and will certainly check out the Hitler pack option

 

[AuntyRinum]

Re: Brendan\'s shrimps

"you didn't press your case as hard when challenged"

OK TCM, I'll try a bit harder.

1 It used to be believed that Snapping Shrimp created sound by clicking their little claws together. It is now known that they close their claws so fast that, by the process of cavitation, they create air bubbles. The bubbles create a crackling sound which is transmitted through water.

2 Propellors spin so fast that, by the process of cavitation, they create air bubbles. The bubbles create a crackling sound which is transmitted through water.

In both cases the sound is similar. Now, you tell me whether you are hearing Snapping Shrimp or a propeller? I think it will depend where you are geographically and what is going on around you..

Personally, I’m warming to KevB’s idea that it is shifting shells or shingle on the bottom. I’d never thought of that.

 

[stevebrassett]

Re: It\'s not shrimp and it\'s not prop noise.

I'm surprised no-one has pointed out the obvious answer. It's people tipping breakfast cereal over the side. We don't get it on the East Coast because bacon and eggs don't react in the same way with salt water, and on the South Coast they're posh, and muesli doesn't make the same noise.

 

[KevB]

Re: Brendan\'s shrimps

[ QUOTE ]
Personally, I’m warming to KevB’s idea that it is shifting shells or shingle on the bottom. I’d never thought of that.


[/ QUOTE ]

Yea, I have a believer.

Brendan, VW toerag is crap - Volvo XC90 T6 much nicer.

 

[BrendanS]

Re: Brendan\'s shrimps

The kids want the XC90 cos of the rear seat sound system! /forums/images/graemlins/smile.gif

 

[KevB]

Re: Brendan\'s shrimps

swmbo wants a XC90 cause it looks nice /forums/images/graemlins/crazy.gif

Have to admit to owning a Volvo, a S80 T6 and the engine and gearbox (steptronic) are fantastic.

 

[BrendanS]

Re: Brendan\'s shrimps

Getting a bit desperate now talking cars, and the thread is still only up to 77 posts!

Think the Touareg looks nicer than the XC90, and much nicer inside. Also V10 twin turbo is the mutts nutts! <g>

 

[Lakesailor]

Re: \'Snap crakle and Pop\' noise from under hull?

It's well known that it's the sound of Osmosis. The speed that water wicks up the fibres compresses the gases in the voids that the incompetent grp layer-upper left and 'pops' the bubble. This leaves an obvious stress fracture in the grp. A rate of more than 100 pops per hour is pretty serious even for a new hull. If it's been happening for more than a couple of days, then imminent sinking is a real probability.

 

[Nauti Fox]

Re: \'Snap crakle and Pop\' noise from under hull?

The Distribution of Snapping Shrimp Noise Near Gladstone, Queensland
Snapping shrimp are commonly found on sea bottoms composed of sheltering materials such as rock and coral, in waters of less than 55 m depth where the water temperature exceeds 11C for much of the year. By snapping closed its large claw the shrimp makes a loud sound. When the shrimp are gathered in large numbers the superposition of these sounds leads to a sustained background noise.

When viewd on a mine hunting sonar screen, the snaps appear as flashes which can form a background clutter, making mine detection difficult. To determine whether this is likely to be a problem in typical mine hunting locations in Australia, a survey was conducted to measure the distribution of snapping shrimp noise within and near a typical harbour. Waters in the vicinity of Gladstone, Queensland, were chosen, and the intensity of the noise generated by the shrimp was measured every nautical mile from Auckland Wharf to the end of the dredged channel leading into the port. Further recordings were taken in five mile steps across Curtis Channel to the edge of the Great Barrier Reef.

The data was analysed between 630 and 12 500 Hz, and showed intense broadband snapping shrimp noise at all sites. The intensity was higher in the harbour and dredged channel than out across the reef. Within the harbour and channel the noise exceeds that which would be expected from wind generated noise during sea state 7. Across the reef the noise exceeds sea state 3 wind generated noise. It is anticipated that the snaps should be evident on a mine hunting sonar screen at all sites investigated in this study.
http://www.dsto.defence.gov.au/publications/2524/

So watch out for mines when you hear em!