# Low voltage loud speakers

#### tylersevery

Joined Sep 22, 2021
6
Hey Everyone,
I know so little about electronics its embarrassing but that is where you come in. I am designing a back country search beacon for lost subjects. In short, I'll have a pole that will have a flashing light and loud as I can find low voltage speaker on it. The idea is to work as an attractant to people that are lost. They don't often wander too far and if the wind can carry the sound, it could guide them back to a trail. That said I need a waterproof speaker in the 100db plus range that can intermittently beep, chirp or honk. The battery (and whole apparatus) will need to be light but last probably 48 hours in cold conditions. We can use a small solar panel to charge it during the day. Thank you in advance for your help.
Any suggestions?

#### BobTPH

Joined Jun 5, 2013
4,260
Horn speakers designed for alarm systems come to mind.

Bob

#### Audioguru again

Joined Oct 21, 2019
4,105
Your idea will permanently deafen anybody who comes close to the noise makers. It will repel smart people.

I was thinking about using a 2.4GHz transmitter and receivers. The receiver antenna is tiny and can be made directional. The receiver could produce a variable frequency tone or an LED bargraph to show the direction to the transmitter.

#### tylersevery

Joined Sep 22, 2021
6
Your idea will permanently deafen anybody who comes close to the noise makers. It will repel smart people.

I was thinking about using a 2.4GHz transmitter and receivers. The receiver antenna is tiny and can be made directional. The receiver could produce a variable frequency tone or an LED bargraph to show the direction to the transmitter.
Thank you for that, I'll start my googling. Oh, and the idea is to be VERY loud, I want the sound to travel for miles at night and when the wind is low. Needs to overpower the wilderness.

#### LowQCab

Joined Nov 6, 2012
1,611
Your scenario doesn't really explain the entire situation.
Are You talking about having this Light and Noise-maker located at a "Base-Camp" ?
What will turn it on ?

A Flashing-Light won't get very far unless it's mounted on top of

The wind can easily "blow-away" Higher-Frequency Sounds,
so You need a really large "PA-Horn", (or 3 or 4 of them since they are directional),
and simply create "clicks" which depend upon the
natural Resonant-Frequency of the large Horn,
which will probably be around ~500-Hz,
(200-Hz would be better but the Horn size would start getting over 5-feet long and
they would have to be custom built $$). They're not cheap at around ~100.oo each. You could power 4 of them for several days on a Car-Battery with 1-"click" every ~5-seconds or so. The maximum Range with this sort of setup would be approximately a ~3-mile radius, with moderate to low ambient wind noise. Heavy Forestation will kill the sound very quickly, and may easily cut the coverage in half. Why not just teach people how to use GPS on their Cell-Phone ? . . . #### Ian0 Joined Aug 7, 2020 4,094 Is this for the benefit of people who have gone out into the wilderness for quiet and tranquility to escape the noise of the city? #### Marjorie62 Joined Sep 23, 2021 2 Constant-voltage speaker systems refer to networks of loudspeakers which are connected to an audio amplifier using step-up and step-down transformers to simplify impedance calculations and to minimize power loss over the speaker cables. They are more appropriately called high-voltage audio distribution systems.[1] The voltage is constant only in the sense that at full power, the voltage in the system does not depend on the number of speakers driven #### Juhahoo Joined Jun 3, 2019 257 Hey Everyone, I know so little about electronics its embarrassing but that is where you come in. I am designing a back country search beacon for lost subjects. In short, I'll have a pole that will have a flashing light and loud as I can find low voltage speaker on it. The idea is to work as an attractant to people that are lost. They don't often wander too far and if the wind can carry the sound, it could guide them back to a trail. That said I need a waterproof speaker in the 100db plus range that can intermittently beep, chirp or honk. The battery (and whole apparatus) will need to be light but last probably 48 hours in cold conditions. We can use a small solar panel to charge it during the day. Thank you in advance for your help. Any suggestions? Constant high pressure beep or sound in the wilderness?! Why not just use of a compass and a map instead of creating unnecessary noise ? People have cell phones these days with GPS, why this sound-solution is necessary? Its like going back in time when boats had light houses, people used smoke for communication etc. #### BobTPH Joined Jun 5, 2013 4,260 Thank you for that, I'll start my googling. Oh, and the idea is to be VERY loud, I want the sound to travel for miles at night and when the wind is low. Needs to overpower the wilderness. This s a non starter for obvious reasons. You would have hikers and campers coming after you with their Bowie knives! Not to mention the hunters. Bob #### Yaakov Joined Jan 27, 2019 3,966 Hey Everyone, I know so little about electronics its embarrassing but that is where you come in. I am designing a back country search beacon for lost subjects. In short, I'll have a pole that will have a flashing light and loud as I can find low voltage speaker on it. The idea is to work as an attractant to people that are lost. They don't often wander too far and if the wind can carry the sound, it could guide them back to a trail. That said I need a waterproof speaker in the 100db plus range that can intermittently beep, chirp or honk. The battery (and whole apparatus) will need to be light but last probably 48 hours in cold conditions. We can use a small solar panel to charge it during the day. Thank you in advance for your help. Any suggestions? In what case would this be deployed and turned on? Is it for specific instances of lost people? Thread Starter #### tylersevery Joined Sep 22, 2021 6 Your scenario doesn't really explain the entire situation. Are You talking about having this Light and Noise-maker located at a "Base-Camp" ? What will turn it on ? A Flashing-Light won't get very far unless it's mounted on top of a ~300-foot tall Broadcasting-Tower. The wind can easily "blow-away" Higher-Frequency Sounds, so You need a really large "PA-Horn", (or 3 or 4 of them since they are directional), and simply create "clicks" which depend upon the natural Resonant-Frequency of the large Horn, which will probably be around ~500-Hz, (200-Hz would be better but the Horn size would start getting over 5-feet long and they would have to be custom built$$$). They're not cheap at around ~$100.oo each.
You could power 4 of them for several days on a Car-Battery with
1-"click" every ~5-seconds or so.

The maximum Range with this sort of setup would be approximately a ~3-mile radius,
with moderate to low ambient wind noise.
Heavy Forestation will kill the sound very quickly,
and may easily cut the coverage in half.

Why not just teach people how to use GPS on their Cell-Phone ?
.
.
.
The last line of your reply is not so easy. But since that is impossible, I am moving to the probable side. There are plenty of instances where this would work. From people trying to navigate snow fields to get down to people stuck in a valley that can still look up. The terrain will always vary but one constant is if we could get something like this out quickly, it is possible to retrieve someone faster. We have to do our best with what fits in our backpacks.

#### Yaakov

Joined Jan 27, 2019
3,966
This paper (and the ones they cite in it) are interesting. My experience suggests that higher frequency sounds will get more attention over greater distances but critically localization is best with low frequencies (125Hz to 500Hz). Obviously you want to get the attention of people but localizing higher frequencies can be difficult. I have a great deal of experience with this because of being a bird photographer and trying to find the birds calling in a tree.

It seems that you will be best off using something broadband in those two ranges. Bursts will save battery. I think you will need to do some extensive field testing to optimize it.

High frequency drivers of decent efficiency can be reasonably small but generating a decent SPL at 125Hz-500Hz will require a larger transducer. Maybe using a purpose built sounder, like a Sonalert, which is both very loud and very efficient thanks to optimization, in conjunction with some sort of driver resonant at the lower frequency possibly in a transmission line enclosure to reduce size, would work.

As far as a visual indicator, I might look first at fire alarm annunciators (whose sounders might actually be useful as well) since they are already packaged up and are already designed for audiovisual alerting. I might be as simple as getting four fire alarms annunciators and mounting them at 0°, 90°, 180°, and 270° on a collapsable mast of the sort used for temporary antenna installations or even a 'painter's pole' with guy lines for support.

You'll almost certainly want an MCU to control the device, possibly even with wireless remote control.

#### Lo_volt

Joined Apr 3, 2014
240
localization is best with low frequencies (125Hz to 500Hz).
Makes me think something that starts out at a lower frequency and increases it as it goes might be the answer. As low frequencies are energy intensive and drain the battery quicker, keep that part of the sound very short.

Seems to me that a fire alarm sounder would be the way to go. Our facilities guys were testing the fire alarms in our building a while back. We were told to ignore the alarms and stay put. Staying put was easy, ignoring the alarm was painful. One of my techs measured the sound pressure at just under 100 dB. Fortunately he had a stash of earplugs to hand out.

Wheelcock is the brand and here's a link to the speakers used in our building.

https://koetterfire.com/products/460-030-WL04.php

I'd suggest that you give the Koetter Fire folks a call to see if they have something that can be battery powered and portable. Look around, as well, for other vendors.

#### Yaakov

Joined Jan 27, 2019
3,966
Makes me think something that starts out at a lower frequency and increases it as it goes might be the answer. As low frequencies are energy intensive and drain the battery quicker, keep that part of the sound very short.

Seems to me that a fire alarm sounder would be the way to go. Our facilities guys were testing the fire alarms in our building a while back. We were told to ignore the alarms and stay put. Staying put was easy, ignoring the alarm was painful. One of my techs measured the sound pressure at just under 100 dB. Fortunately he had a stash of earplugs to hand out.

Wheelcock is the brand and here's a link to the speakers used in our building.

https://koetterfire.com/products/460-030-WL04.php

I'd suggest that you give the Koetter Fire folks a call to see if they have something that can be battery powered and portable. Look around, as well, for other vendors.
Inexpensive, standardized annunciators are available, even on Amazon. There are outdoor models that can handle weather. They include strobes and optimized sounders and while they may not be ideal for localization (not their intended purpose) they may be practically effective, testing would be easy.

They usually run from 24V, I think. So some kind of decent lithium battery might be good.

#### LowQCab

Joined Nov 6, 2012
1,611
I still haven't seen a definitive explanation of
the Who, What, Where, When, and How, of this whole project.
Exactly what problem needs to be solved here ?
Are we supposed to guess ?
.
.
.

#### GetDeviceInfo

Joined Jun 7, 2009
1,954
Agree. We carry an inreach on all our sheep hunts.
It doesnt protect us from bears though, which in Kananaskis is a growing problem with grizzlies.
Personally, I would look at some type of boom stick. Something powered by a cartridge. The classic 3 shot discharge still holds true for SOS. Double up as a walking stick, works when wet.

#### tylersevery

Joined Sep 22, 2021
6
This s a non starter for obvious reasons. You would have hikers and campers coming after you with their Bowie knives! Not to mention the hunters.

Bob
I don't think so, most search areas are closed once a search kicks off. But thank you for your reply.

#### BobTPH

Joined Jun 5, 2013
4,260
And most people who are being searched for are dead or immobilized, not simply lost.

Bob