AuntyRinum
Well-Known Member
Re: er not the props
tcm - Not prop noise from your own boat! Prop noise from a passing boat.
tcm - Not prop noise from your own boat! Prop noise from a passing boat.
'Snap crakle and Pop' noise from under hull?
- Thread starter Anthony
- Start date
Swagman
Well-Known Member
Sad Trend
Hope this is not taken wrongly but it seems to me more and more threads turn into respondants commenting upon each others expertise or knowledge - as opposed to providing good advice to the person who asked the orginal question.
I for one thank BrendanR for publishing the link to the sounds I've certainly experienced - and in doing so clarifying for me the source.
So come on guys - why not put all the handbags away or at least stop swinging them at one another - and get back to using this forum for what it is intended - practical advice.
Cheers
JOHN
Hope this is not taken wrongly but it seems to me more and more threads turn into respondants commenting upon each others expertise or knowledge - as opposed to providing good advice to the person who asked the orginal question.
I for one thank BrendanR for publishing the link to the sounds I've certainly experienced - and in doing so clarifying for me the source.
So come on guys - why not put all the handbags away or at least stop swinging them at one another - and get back to using this forum for what it is intended - practical advice.
Cheers
JOHN
tcm
...
Re: er not the props
ah understood.
But i get this at anchor when there are no other boats for miles - or the same noise in marina if other boats are going past a fair bit eg mid-morning. INothehr words not dependent upon lots or zero nerarby boats. It is a reasonably constant-volume chompity chompity (in the same as are ciccadas on a warm night in the med) - whereas a passing boat noise wd come in and go away? An explanation such as a lot of small creatures fairly nearby (ie on the hull) make sense.
ah understood.
But i get this at anchor when there are no other boats for miles - or the same noise in marina if other boats are going past a fair bit eg mid-morning. INothehr words not dependent upon lots or zero nerarby boats. It is a reasonably constant-volume chompity chompity (in the same as are ciccadas on a warm night in the med) - whereas a passing boat noise wd come in and go away? An explanation such as a lot of small creatures fairly nearby (ie on the hull) make sense.
AuntyRinum
Well-Known Member
Re: \'Snap crakle and Pop\' noise from under hull?
It's propellor noise from other boats and it's easy to prove. Next time you are on a boat which is anchored, tied up in a marina or wherever, it doesn't matter as long as the sea is calm, do the following:
1 Wait until a boat under power passes within 50 to 100 yards of you.
2 As the boat passes, get into the bilge of your boat where you can see the inside of the hull below the waterline.
3 Make sure there is no extraneous noise.
4 Listen to the crackling sound through the hull.
It happens every time and this is the noise you hear at night when it's quiet, as boats pass. It seems to be more obvious on fibreglass boats, presumably they transmit the sound better.
I have no explanation, only a theory that it's cavitation noise, and I can do no more than tell you its source.
It's propellor noise from other boats and it's easy to prove. Next time you are on a boat which is anchored, tied up in a marina or wherever, it doesn't matter as long as the sea is calm, do the following:
1 Wait until a boat under power passes within 50 to 100 yards of you.
2 As the boat passes, get into the bilge of your boat where you can see the inside of the hull below the waterline.
3 Make sure there is no extraneous noise.
4 Listen to the crackling sound through the hull.
It happens every time and this is the noise you hear at night when it's quiet, as boats pass. It seems to be more obvious on fibreglass boats, presumably they transmit the sound better.
I have no explanation, only a theory that it's cavitation noise, and I can do no more than tell you its source.
bbg
Well-Known Member
Re: Sad Trend
Agree about the sad trend ...
The link that BrendanS posted has both snapping shrimp and a diesel engine 650 yards away - with snapping shrimp in the background.
I have heard the sound as well, both in Med and Caribbean, and assumed it was creatures of some kind - fish snapping at coral, crabs etc. I also assumed that it did not need to be right next to the boat (i.e. could be up to 50 metres away or more) because a) noise propogates so well in water b) the sound was so constant and c) there seemed to be so many sources.
I am glad to have my suspicions confirmed. Snapping shrimp is the explanation I will give to others from now on.
Agree about the sad trend ...
The link that BrendanS posted has both snapping shrimp and a diesel engine 650 yards away - with snapping shrimp in the background.
I have heard the sound as well, both in Med and Caribbean, and assumed it was creatures of some kind - fish snapping at coral, crabs etc. I also assumed that it did not need to be right next to the boat (i.e. could be up to 50 metres away or more) because a) noise propogates so well in water b) the sound was so constant and c) there seemed to be so many sources.
I am glad to have my suspicions confirmed. Snapping shrimp is the explanation I will give to others from now on.
tringa
Active Member
Naughty
[ QUOTE ]
I don't care how offended you are
[/ QUOTE ]
Offending people is definitely not permitted. Surely you knew that?
Funny thing really. Regular outbursts in the Lounge against political correctness, most of which represents an attempt, however misguided, to avoid giving offence, combined with outrage against anything that might give offence.
There's nowt so queer etcetera /forums/images/graemlins/confused.gif
[ QUOTE ]
I don't care how offended you are
[/ QUOTE ]
Offending people is definitely not permitted. Surely you knew that?
Funny thing really. Regular outbursts in the Lounge against political correctness, most of which represents an attempt, however misguided, to avoid giving offence, combined with outrage against anything that might give offence.
There's nowt so queer etcetera /forums/images/graemlins/confused.gif
Swagman
Well-Known Member
Engine Noise?
Can't help myself in adding this fact - to try and put the 'it's an engine / prop noise' view into perspective.
I've heard this noise all night parked up in a coral atoll with closest civilisation (ie other island 350 miles away) and never another boat of any size in sight.
Guess others will now say it must have been a submarine parked up the other side of the atoll on tickover...........
Hopefully enough said.
JOHN
Can't help myself in adding this fact - to try and put the 'it's an engine / prop noise' view into perspective.
I've heard this noise all night parked up in a coral atoll with closest civilisation (ie other island 350 miles away) and never another boat of any size in sight.
Guess others will now say it must have been a submarine parked up the other side of the atoll on tickover...........
Hopefully enough said.
JOHN
tcm
...
Re: \'Snap crakle and Pop\' noise from under hull?
um, with respect and logically speaking your test proves no such thing. The noise described could be present before and after the boat passes - but your test requires one to listen only as and when a boat passes - it sets out to confirm the pre-decided cause.
A better test is to wait until there are NO boats passing and then listen - in other words one shoud try and prove the hypothesis by attempting to *disprove* it. Hence, essentially, "the exception proves the rule".
In this case the lack of boats passing on even just ONE occassion would prove it cannot be prop noise. Others do report the noise without any boats moving nearby.
If it was cavitation then it would be surely accompanied by the rythm of the props. And would there *always* be cavitation if a prop turns, even at very low speed? And surely, wouldn't the frequency/pitch or amplitude/volume of the noise vary quite dramatically if it were prop noise? The noise made by a 6inch diameter prop 20mteres away ould not be the same as a 1metre prop say 75 metres away. Yet the noise made by throng of nearby tiny ainmals would be always about the same volume and pitch - as this noise is?
um, with respect and logically speaking your test proves no such thing. The noise described could be present before and after the boat passes - but your test requires one to listen only as and when a boat passes - it sets out to confirm the pre-decided cause.
A better test is to wait until there are NO boats passing and then listen - in other words one shoud try and prove the hypothesis by attempting to *disprove* it. Hence, essentially, "the exception proves the rule".
In this case the lack of boats passing on even just ONE occassion would prove it cannot be prop noise. Others do report the noise without any boats moving nearby.
If it was cavitation then it would be surely accompanied by the rythm of the props. And would there *always* be cavitation if a prop turns, even at very low speed? And surely, wouldn't the frequency/pitch or amplitude/volume of the noise vary quite dramatically if it were prop noise? The noise made by a 6inch diameter prop 20mteres away ould not be the same as a 1metre prop say 75 metres away. Yet the noise made by throng of nearby tiny ainmals would be always about the same volume and pitch - as this noise is?
AuntyRinum
Well-Known Member
Re: \'Snap crakle and Pop\' noise from under hull?
tcm you may be right.
What I do know though, is that the sound occurs when boats pass. I don't know the maximum range that it can be heard from, but I do know that I've never heard it in UK waters or the Med unless boats are passing. Having said that, I can't be spending too much time with my head in the bilge listening.
I have heard this in The Seychelles without boats passing and will accept that in that case it may be Snapping Shrimps as they are found in tropical waters, but I'm still not convinced that they can be heard without the aid of a hydrophone.
Mantis Shrimps which are snappers have been found in UK waters but I doubt in sufficent numbers to be heard without a hydrophone.
So after years of puzzling about this I still think it's passing boats as far as UK and Med are concerned. If anybody can prove that it's not, then I'd be very interested if they would post their views as I'd like a definitive answer.
tcm you may be right.
What I do know though, is that the sound occurs when boats pass. I don't know the maximum range that it can be heard from, but I do know that I've never heard it in UK waters or the Med unless boats are passing. Having said that, I can't be spending too much time with my head in the bilge listening.
I have heard this in The Seychelles without boats passing and will accept that in that case it may be Snapping Shrimps as they are found in tropical waters, but I'm still not convinced that they can be heard without the aid of a hydrophone.
Mantis Shrimps which are snappers have been found in UK waters but I doubt in sufficent numbers to be heard without a hydrophone.
So after years of puzzling about this I still think it's passing boats as far as UK and Med are concerned. If anybody can prove that it's not, then I'd be very interested if they would post their views as I'd like a definitive answer.
RupertW
Well-Known Member
Re: \'Snap crakle and Pop\' noise from under hull?
So, to follow the logic, tropical waters may have dolphins but after years of puzzling what the identical-looking creatures in the UK might be I've concluded that the grey bow-leaping things must be mutant binbags. Please prove to me that they're not.
So, to follow the logic, tropical waters may have dolphins but after years of puzzling what the identical-looking creatures in the UK might be I've concluded that the grey bow-leaping things must be mutant binbags. Please prove to me that they're not.
StugeronSteve
Well-Known Member
Re: \'Snap crakle and Pop\' noise from under hull?
Possibly correct! We made a diversion half way across Lyme bay to investigate what appeared, at binocular range, to be a seal in the water. Closer in it started to look like a guy doing front crawl and we started to get concerned. Close up it proved to be a bin bag caught up on a floating log.
Possibly correct! We made a diversion half way across Lyme bay to investigate what appeared, at binocular range, to be a seal in the water. Closer in it started to look like a guy doing front crawl and we started to get concerned. Close up it proved to be a bin bag caught up on a floating log.
jerryat
Well-Known Member
Re: Sad Trend
It IS small crustceans not prop noise. We have had it occur in totally isolated anchorages, with no near (or far) craft under motor.
In my experience, the sound of a propellor, heard through the hull, is totally different and easily distinguishable. A diver friend of mine, interested in this noise on his own boat, confirmed that small prawn like animals were nibbling away the minute weed type growth on his hull.
We were very relieved to hear this at the time, 'cos I'd had dreadful thoughts about faulty wiring and the like as the crackling sounds very much like arcing.
Prop noise is very regular, pulsating and yes, can give a crackly effect, but the noise we've experienced is certainly NOT regular and varies in 'loudness' over very short periods.
Cheers Jerry
It IS small crustceans not prop noise. We have had it occur in totally isolated anchorages, with no near (or far) craft under motor.
In my experience, the sound of a propellor, heard through the hull, is totally different and easily distinguishable. A diver friend of mine, interested in this noise on his own boat, confirmed that small prawn like animals were nibbling away the minute weed type growth on his hull.
We were very relieved to hear this at the time, 'cos I'd had dreadful thoughts about faulty wiring and the like as the crackling sounds very much like arcing.
Prop noise is very regular, pulsating and yes, can give a crackly effect, but the noise we've experienced is certainly NOT regular and varies in 'loudness' over very short periods.
Cheers Jerry
bobupanddown
Well-Known Member
Re: Sad Trend
I've heard this noise quite a lot at night whilst anchored. I came to the conclusion that it was probably the batteries bubbling after being charged at a high rate. Especially as the noise seemed loudesst near to the battery compartment.
I now wait for the inevitable reply from somebody on a boat with no batteries!!
I've heard this noise quite a lot at night whilst anchored. I came to the conclusion that it was probably the batteries bubbling after being charged at a high rate. Especially as the noise seemed loudesst near to the battery compartment.
I now wait for the inevitable reply from somebody on a boat with no batteries!!
kimhollamby
Well-Known Member
Ah but Brendan and Brett H...
...I do care.
i might be a part-time attendant these days but as Keith is not around at the moment let me remind you both of the rules regarding abusive language in relation to other users.
...I do care.
i might be a part-time attendant these days but as Keith is not around at the moment let me remind you both of the rules regarding abusive language in relation to other users.
tcm
...
Re: \'Snap crakle and Pop\' noise from under hull?
I am at the disadvantage of not being able to click on the noise-effect thing cos my puter doesn't have the sound card thing or the speakers are bust/whatever.
My only experience is of hearing the definite "snap crackle and pop" most definitely. Further I am probably a bit more keen on bilge crawling/sitting than most - I have massive bilges with lots of things innem with plenty of room to sit about tinkering and staring into space - so i spend a fair bit of time down there and a *bit* of that time thinking "I wonder what that snap crackle pop noise is?" but then carry on twiddling with various valves.
Since there just can't be that many boats moving around for as long as i'm sitting in the bilges (cos the noise would come and go) then the snapping prawn is a possible.
However, partly cos of lack of soundcard and lack of research i can't be sure. If it's snapping prawns then the southern french med must be flippin CRAWLING with the prawn critturs cos i can't easily remeber a time when the snap crack pop noise wasn't there. I wonder if Brendan can advise as to whether the micro-prawns hitch a ride on the boat and then continue immediate scoffing? Or do they rush over as soon as i anchor? Or do they sulkily wait for me to return? The barnacle farm boat next to me (not moved for praps five years, busted engines) would be a greast place for barnacle-grazers to hang out i suppose.
I am almost certain that it isn't the batteries bubbling - the noise is too insistent for that and looking closey at the batteries i'm not noticeable "closer" to the noise
I hope we can generate a bit more light than heat anyway.
I am at the disadvantage of not being able to click on the noise-effect thing cos my puter doesn't have the sound card thing or the speakers are bust/whatever.
My only experience is of hearing the definite "snap crackle and pop" most definitely. Further I am probably a bit more keen on bilge crawling/sitting than most - I have massive bilges with lots of things innem with plenty of room to sit about tinkering and staring into space - so i spend a fair bit of time down there and a *bit* of that time thinking "I wonder what that snap crackle pop noise is?" but then carry on twiddling with various valves.
Since there just can't be that many boats moving around for as long as i'm sitting in the bilges (cos the noise would come and go) then the snapping prawn is a possible.
However, partly cos of lack of soundcard and lack of research i can't be sure. If it's snapping prawns then the southern french med must be flippin CRAWLING with the prawn critturs cos i can't easily remeber a time when the snap crack pop noise wasn't there. I wonder if Brendan can advise as to whether the micro-prawns hitch a ride on the boat and then continue immediate scoffing? Or do they rush over as soon as i anchor? Or do they sulkily wait for me to return? The barnacle farm boat next to me (not moved for praps five years, busted engines) would be a greast place for barnacle-grazers to hang out i suppose.
I am almost certain that it isn't the batteries bubbling - the noise is too insistent for that and looking closey at the batteries i'm not noticeable "closer" to the noise
I hope we can generate a bit more light than heat anyway.
catmandoo
Well-Known Member
Re: \'Snap crakle and Pop\' noise from under hull?
I understood tht the noise was generated by fish
I understood tht the noise was generated by fish
Steve Clayton
Well-Known Member
Re: \'Snap crakle and Pop\' noise from under hull?
So guys and gals:
So guys and gals:
absit_omen
Well-Known Member
Re: Steve_Clayton
Steve, you missed out 'Neither of the above' !!
Steve, you missed out 'Neither of the above' !!
Steve Clayton
Well-Known Member
Re: Steve_Clayton
I can't modify/add to the vote options.
You do another one and then I'll delete my post.
I can't modify/add to the vote options.
You do another one and then I'll delete my post.
bilbobaggins
N/A
Re: \'Snap crakle and Pop\' noise from under hull?
Agh! Shame..... etcetera....
I seem to recall that the well-known boats' degenerative disease 'Polyestermites' was first publicised by a fondly-remembered past-editor of Practical Boat Owner. He was credited with linking the problem with the underwater sounds being discussed here.
From time to time - especially in a quiet anchorage after dinner, with the uisge beatha slowly warming some new friends - when the cracklinmg is heard beneath the hull, a comment from one to another re these 'pesky polyestermites' gets newbies going.
Lore of the sea.....
/forums/images/graemlins/cool.gif /forums/images/graemlins/cool.gif /forums/images/graemlins/smile.gif
Agh! Shame..... etcetera....
I seem to recall that the well-known boats' degenerative disease 'Polyestermites' was first publicised by a fondly-remembered past-editor of Practical Boat Owner. He was credited with linking the problem with the underwater sounds being discussed here.
From time to time - especially in a quiet anchorage after dinner, with the uisge beatha slowly warming some new friends - when the cracklinmg is heard beneath the hull, a comment from one to another re these 'pesky polyestermites' gets newbies going.
Lore of the sea.....
/forums/images/graemlins/cool.gif /forums/images/graemlins/cool.gif /forums/images/graemlins/smile.gif