Author Topic: Establishing a sound connection with insufficient people....  (Read 530 times)

Offline tim.rose2

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Establishing a sound connection with insufficient people....
« on: March 30, 2021, 08:10:22 pm »
As the title says really.  Anyone got any tried and tested methods of testing for sound connections between caves when you've insufficient people to have somebody each side?  I'm thinking along the lines of...
1. Enter cave 1, leave device making noise and exit cave.
2. Enter cave 2 and see if you can hear it.

The 'device' will need to be loud (i.e. equivalent of someone shouting) and be able to make said noise for a couple of hours to give time to get between the locations.  It will need to be cave proof (but not waterproof) and not matter if I leave it for a week or two should I not bother to go back into cave 1 on the same day to retrieve it.  A bonus would be if the device also emitted light, though obviously leaving a torch shining is the obvious solution to this.  Ideally something dirt cheap.

All ideas welcome though I'm particularly interested to hear from anyone who's had success doing this sort of thing.

Cheers in advance.
Tim

Offline Fishes

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Re: Establishing a sound connection with insufficient people....
« Reply #1 on: March 30, 2021, 08:34:35 pm »
I've seen this kind of thing used in the past.

https://portek.co.uk/portfolio/double-bang-banger-ropes/

They can make quite a bit of smoke though and probably aren't bat friendly.

Offline Bob Mehew

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Re: Establishing a sound connection with insufficient people....
« Reply #2 on: March 30, 2021, 08:36:38 pm »
I would recommend snow avalanche transmitter & receiver, although the signal is radio rather than sound.  We managed to get proof of limited distance even though there was only solid rock between us.  And they kept going for days.  Otherwise possibly a rape alarm.  But you will have to mod it to put in a bigger battery to get the life time you want.  (That should not be to difficult and at £10 for one it should be worth a punt.)

Offline pwhole

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Re: Establishing a sound connection with insufficient people....
« Reply #3 on: March 30, 2021, 08:40:22 pm »
I would hazard a guess that whatever you use to transmit will need to be low-frequency to have a chance of traveling through the rock - you may end up feeling it rather than hearing it, but that's fine. I've heard Hope Cement Quarry letting off a blast a few times inside Peak Cavern now, but I never heard the warning siren five minutes before!

If it wasn't for the possibility of leaving it in for a week, I'd suggest a boom-box playing drum n'bass. Alternatively, still leave a boom-box playing drum n'bass in, but also include some well-fed hippy dude and a UV light and tell him to keep changing the batteries until you return the next weekend ;)

Online ChrisJC

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Re: Establishing a sound connection with insufficient people....
« Reply #4 on: March 30, 2021, 09:03:41 pm »
A piezo sounder / buzzer, at about 2kHz (where human hearing is at its most sensitive). They take very little power, so a decent lead acid battery and it would  last for ages.

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Offline tim.rose2

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Re: Establishing a sound connection with insufficient people....
« Reply #5 on: March 30, 2021, 09:33:28 pm »
There's two places I'd like to do this.  Both are likely to be 'open' passage through too tight rift so I don't think (hope) it'll need to penetrate solid rock.  Could be a few meters though.  When we tested Rumble to Grove Cliff Fissure it was around 20 m with some height variation involved and that was the limit of being able to shout at each other.  I'd hope both of these are less than 10 m and possibly only a couple so it might turn out loud is not required.

My first thought was some of Phil Collins finest work, a very cheap MP3 player and speaker but that won't be very loud. 

The piezo sounder idea looks perfect.  I know bugger all about electronics something like this + a 9 volt battery?
https://www.ebay.co.uk/itm/Piezo-Buzzer-Sounder-3-12V-DC-85Db-BUY-TWO-GET-A-THIRD-FREE/122923029230?hash=item1c9ec892ee:g:3IIAAOSw42JZI-~~

Would that work?  How long would it last?

Online ChrisJC

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Re: Establishing a sound connection with insufficient people....
« Reply #6 on: March 30, 2021, 09:58:46 pm »
I was thinking something like this:
https://uk.rs-online.com/web/p/piezo-buzzer-components/1367925/
and a 12V battery like this:
https://ebay.us/hbxVni

The buzzer takes 50mA, and the battery is 7Ah, so that would last for about 140 hours. Enough time to place it, exit, pop into the Hunters for a beer, then go somewhere else and have a listen.

Chris.

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Offline tim.rose2

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Re: Establishing a sound connection with insufficient people....
« Reply #7 on: March 30, 2021, 10:07:44 pm »
Thanks Chris looks like a great idea.  As a really cheap and smaller option would this work?
https://www.amazon.co.uk/WMYCONGCONG-Electronic-Sounder-Continuous-Connector/dp/B07J6Q6QMT/ref=sr_1_4?crid=39P4UKIZCD9KL&dchild=1&keywords=piezo+buzzer&qid=1617137148&sprefix=piezo+bu%2Caps%2C171&sr=8-4
Plus a 9v battery?
Looks like a 9v battery is 500 mAh so at 15mA should last 30 hrs.  Would only need a couple of hours.


Offline mrodoc

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Re: Establishing a sound connection with insufficient people....
« Reply #8 on: March 31, 2021, 01:02:27 pm »
The avalanche radio concept as Bob suggests seems to work and has been used successfully in Scotland on a link dig/

Online ChrisJC

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Re: Establishing a sound connection with insufficient people....
« Reply #9 on: March 31, 2021, 05:12:57 pm »
Thanks Chris looks like a great idea.  As a really cheap and smaller option would this work?
https://www.amazon.co.uk/WMYCONGCONG-Electronic-Sounder-Continuous-Connector/dp/B07J6Q6QMT/ref=sr_1_4?crid=39P4UKIZCD9KL&dchild=1&keywords=piezo+buzzer&qid=1617137148&sprefix=piezo+bu%2Caps%2C171&sr=8-4
Plus a 9v battery?
Looks like a 9v battery is 500 mAh so at 15mA should last 30 hrs.  Would only need a couple of hours.

That would work. It would be quieter - I guess you could built it and see if you think it's loud enough.
In fact, those ones will also work at 12V for more loudness if 9V is not enough.

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Offline Rob

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Re: Establishing a sound connection with insufficient people....
« Reply #10 on: March 31, 2021, 07:20:08 pm »
Are mates really this hard to come by?!?
The end is where we start....

Offline tim.rose2

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Re: Establishing a sound connection with insufficient people....
« Reply #11 on: March 31, 2021, 08:00:34 pm »
They can be when the caves are as shit excellent as those on Portland.  Been trying to doing this since the Autumn.  A mixture of lockdowns, poor weather and inability to get the right people together has led me to explore alternatives.

 

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