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Outdoor listening installations Answered

Would appreciate some advice on this project. 
I'm putting together a proposal for a series of outdoor sound installations in a nature park. 

a couple of the installations will be places where you can plug in headphones to listen to certain sounds captured live from a microphone in an interesting place- for example a hydrophone in a pond. 

The plan is that the mic will be hooked up to 3.5 jack sockets and listerners will be able to plug in their own headphones. 

Now obviously there needs to be some amplification because the mic signal level will be far too quiet to hear on headphones. I need a power amp that will be powered through a solar panel. 

My question is, shall I just use a headphone amp, like the Behringer ha400 or make my own power amp circuit? I need to be able to make everything sturdy and fit into a weather proof junction box to protect it from the elements. I have done some experiments with an LM386 power amp module but there was so much background noise and it didn't pick up the mic level at all (may have been a problem with the mic I was using,it was a crappy little lapel mic.- I did get a signal from a piezo disc but it was again really crackly and noisy.) 

If it is best to build a circuit with a power amp module, could people make suggestions of ones that will sound good and clean, and work with stereo headphones. 

Thanks a lot

Ash

Discussions

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AshtonM4

3 years ago

Thanks for the interesting ideas guys. The idea of speakers would be really nice. Either way though I would need to get the extremely low mic level up to an audible line level. Any advice on this?

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Downunder35mAshtonM4

Reply 3 years ago

Circuits for this are no problem, just check for all these "spy" microphones...
Line level is only around 0.7V ;)
For PA systems aroun 1.8 or something...
I don't want to spoil your ideas but did you consider the modern world?
Most smartphones allow bluetooth audio profiles but of course on as the phone being the master.
But you could use a quite simple BT audio tranmitter and corresponding headphones.
This way the power equirements outdoors are kept to a minimum, there are no weather proofing issues and you only need to make sure the headphones are charged.
As an alternative with slightly higher power requirements you could also use a low power radio tranmitter.
This was anyone with a FM radio can listen to it if close enough to the trnasmitter.
Checking of local laws is required for this though....

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Kiteman

3 years ago

OK, slightly not what you were looking for, but why not have speakers?

My local hospital has a sound installation in one of the corridors, but you cannot hear it unless you stand in specific places - low-volume sounds are focussed by clear plastic domes on the ceiling (actually old hairdryer hoods) so that they can be heard by people standing where footprints are painted on the floor.

You could do similar with parabolic-curved walls - have a number of quiet speakers pointing towards the walls, and people standing at the focus of the curve will hear the sound. You could have a long, scalloped wall alongside a footpath, with speakers hidden on the opposite side of the path (in tree stumps, lamp posts etc) - as people walk along the path, they will hear sounds fade in and out.

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Downunder35m

3 years ago

You need microphones and amps designed for the purpose, using standard, wide range mics and a simpe headphone amp won't get you anywhere.
Also be aware that you will need special headphone jacks to withstand the elements, normals one will fail within weeks.

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AshtonM4Downunder35m

Reply 3 years ago

Thanks. I was definitely planning to use specific weatherproof mics and 3.5 jacks, but the power amp is the tricky but as I don't think there is such a thing as a weatherproof microphone amp. However this I can easily put inside a waterproof junction box.

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Downunder35mAshtonM4

Reply 3 years ago

If you step back in time and allow for a slightly less audio quality then you can use a crystal earpiece instead of headphones.
The only use a fraction of the power a standard headphone speaker requires and for most audio applications no amplifier as such is required.
Back in the day the "crystal radio" worked without and power source at all, the enrgy from the radio waves was enough to make it work....