Good day Lily.

I stumbled upon this post of yours.
Have you been able to make any advancement on this topic, or get any feedback from anyone?

I have been asked a similar question by a group, looking at early warning systems for large mammals, like elephants, of possible danger situations.

On my side, it is still a very new project, however, my use case has more to do with the trains that kills the elephants, but we also have a use case for early warning systems to recognize poachers and early warning systems to intercept any possible threat.

So if you are in a position, and willing to share any information, I would like to find out more, if there has been any developments regarding this topic aon your side.

Kind regards 
​Mischa

Hi,

Generating infrasound is generally energy intensive and expensive.  You can google "infra-subwoofer" and despair at the prices!  But those are for audiophiles.  I came across a fan type speaker design a long time ago that I think can be adapted,  Another possibility is to use pyrotechnics to generate infrasound, but that would not be reusable and I suspect development will be even more of a headache.  An intriguing possibility is to use basically a fogger - - those noisy smoky fumigators -- but built to produce the lower frequency.

You should check out Smart Parks (https://www.smartparks.org/) and Hack the Poacher (https://www.hackthepoacher.com/). 

Also - 

Fazil, M., & Firdhous, M. (2018, December). IoT-enabled smart elephant detection system for combating human elephant conflict. In 2018 3rd International Conference on Information Technology Research (ICITR) (pp. 1-6). IEEE.

Shaffer, L. J., Khadka, K. K., Van Den Hoek, J., & Naithani, K. J. (2019). Human-elephant conflict: A review of current management strategies and future directions. Frontiers in Ecology and Evolution, 6, 235.

That last paper is a nice overview of different methods, and they have a section on acoustic strategies.

I've worked on a similar project to try to scare lions away from bomas in Kenya that's pretty much a bunch of stuff from Adafruit rigged together with cheap marine speakers in an overly complicated custom case (picture is of previous generation, new generation in development). We also run LEDs to show various light displays. I imagine you could imitate a muzzle flash to deepen the illusion of gunfire. I'm also happy to discuss things (although I don't think I can match the technical expertise of Freaklabs).

Suraci et al. have published a few papers about the use of an automated behavioral response system for sound playback when triggered by a camera trap. Their methods (see supplementary materials) are entirely open source and I even commissioned an engineer to make a few for me. The only issue is that the MP3 players need a separate battery pack to keep them charged or need to be charged weekly, as the sound runs continuosly since there would otherwise be a delay between the camera trigger and the MP3 player being turned on. This could probably be fiddled with to suit your needs, if the previous options don't work out.

https://besjournals.onlinelibrary.wiley.com/doi/10.1111/2041-210X.12711  

We actually designed Boombox, the audio player shown above, based on the ABRS system by the Suraci paper and with Dr. Meredith Palmer. We made some optimizations on it since the paper advocates an approach to infer when the camera was triggered. We reverse engineered our camera traps and took the actual trigger signal from the trailcam PIR motion sensor. Later, we were contacted by one of the authors of the paper and he mentioned they had come to the same conclusion.

We built the MP3 playback system using a discrete MP3 decoder IC which allowed us more control over playback, power management, and we could pick out the output amplifier to drive the speakers. We knew we would need to put the system to sleep and immediately play sounds on wakeup which most players aren't suited to do.

We also made it so that it's solar rechargeable with lithium-ion batteries so that it could last in the field as long as possible. Unfortunately we couldn't use that feature because there's no point in outlasting the trailcams. But for this application, it seems we might be able to use the solar recharging functionality. 

We've volunteered for a possible TechTutors season 2 workshop on open source MP3 playback and recording with Arduino.  We're waiting to discuss it with Steph and Ellie. If this sounds interesting, please let us know.