Hi all,
I am a new user to passive acoustic monitors generally, and was looking at purchasing an audiomoth. I have a couple of questions that I hope the community here may have expereince in or at least suggestions to push me in the right direction. We are planning to deploy audiomoths in conjunction with camera traps to create an array of monitoring stations to monitor terrestrial mammals, the bird community, and anthropogenic disturbance such as vehicle noise and gunshots. The environment is very arid desert, where summer temperatures can exceed 50 degrees Celsius at their peak.
This has lead me to a few questions;
- Could the ambient temperatures represent a problem for the audiomoths in the summer? We plan to house them in the IPX7 Case (https://www.labmaker.org/products/audiomoth-ipx7-case)
- Is there a way to configure the audiomoths to record at dawn and dusk to detect bird species when they are most likely to be vocal, as well as having a threshold mode where triggers such as vehicle noise and gun shots wake the audiomoth from sleep and record them? I can see from the manual that it has a triggered recording and a schedule mode, but can one device run both modes simultaneously?
- Finally I saw on another post that it is potentially possible to integrate the audiomoth with a solar panel (https://www.openacousticdevices.info/support/device-support/integrating-solar-panels-with-batteries-to-audiomoth). Has anyone successfully done this and can confirm that I would need to purchase all of the components listed here (https://www.waveshare.com/catalogsearch/result/?q=solar+power)? If so would they be willing to provide some guidance on how to correctly attach the relevant components.
Thanks in advance for your time.
Tom Bruce
21 January 2025 5:06pm
Hi Tom,
For the solar panel stuff - if you want a more off-the-shelf solar panel option, you could also check out the SongMeter + solar panel from Wildlife Acoustics, or the Solar BAR from Frontier Labs. What is the specific reasoning behind having a solar panel - do they need to be running for super long amounts of time? SongMeters and BARs have rechargeable lithium battery options that allow for longer recording periods than the Audiomoth. They are each more expensive than Audiomoth though.
Temperature is definitely a factor, not only for the recorders themselves but also for the batteries (make sure to look at the temperature ratings for the batteries you're using) and SD cards (I recommend SanDisk ExtremePro). I would also recommend putting them in shaded areas, or I know some folks have constructed wooden "roofs" that they attach above the recorders to provide shade so they're not in direct sunlight. The SongMeters and BARs both have operating temperature ranges that would be ok for 50C (per their websites). I can't see temperature specs on the AM website. If you do go with the Audiomoths, I would recommend posting in the Audiomoth Support Forum to see if anyone has field experience in similar situations.
And for the scheduling, I believe AMs only let you set an amplitude threshold for a given schedule, so if you set it to record at dawn and dusk it would just do the amplitude threshold during dawn and dusk. So what you're suggesting wouldn't be possible, unless there was a way for you to hard-code something into custom firmware. SMs and BARs have a bit more flexibility in their scheduler apps but I'm not sure if it would allow for what you're hoping. But in any case, you would probably want to be running a different sample rate for those different schedules, in which case you'd need 2 recorders. A common similar use case is when people want to record bats and also birds, typically you would use 2 recorders, one running the ultrasonic sample rate with a threshold that just is at night (bats), while the other runs a regular sample rate during the day without threshold. So I'd personally recommend using 2 recorders for the 2 different use cases.
Hope that all helps!
Carly
24 January 2025 3:05pm
Echoing off what @carlybatist said, one thing to consider is that temperature/sunlight might degrade the waterproof acoustic membrane over time, which may compromise the case. Having a roof over the top would be helpful to avoid the effects of both of these. When you service the recorders, don't forget to replace the acoustic membranes. You can buy extra from Open Acoustic Devices. Depending on where you are located (my experience is in the Southwestern US), consider any desert mammals that might chew on your tasty station equipment as well. If you have to connect solar panels via any cables, I suggest encasing them in PVC or similar to reduce the likelihood of rodents using your cables as a chew toy, and if you place your device on a pole/post, consider some architecture to reduce any animal climbing up the pole/post. We have quite the graveyard of equipment destroyed by animals!
25 January 2025 7:24am
You have a bit of a feedback problem where you want solar for the panel but want to reduce heating of the device itself. From a technical level, simple lithium batteries can go up to 60 C (check with the datasheet) but generally, you shouldn't charge them above 45 C since that could degrade the battery. That makes it a bit problematic since heat and direct solar go hand-in-hand. Many solar charging circuits have temperature protection built in as to not charge a battery when above a certain temperature but you need to check with the system you use.
A recommendation on installation is that for whatever you use, if the solar panel isn't integrated into the device, you should position it so it shades the recorder. You can also hide the recorder under shade while keeping the solar panel exposed. Any shading of a solar panel, including partial, will drastically reduce the energy harvesting performance. If the panel is designed with solar cells in series, 20% shading can lead to 80% power reduction (this is all dependant on the solar cell architecture).
Technically, waking a system up from a loud sound isn't that difficult and there are microphones that have that feature built in. Where it gets tricky is if you not only want to wake up from a sound but also have a full recording of that sound. Generally, a system would need to buffer that data prior to detection and then save it which could be a bit power hungry (i.e., the system is always active or in a reduced listening mode). I'm not sure if any commercial device supports this but its not hard to architect if you end up designing your own system and if you have the power budget to do so. Scheduling recordings is more-and-more supported across the board of acoustic recorders.
Lastly, its a dry arid climate so the solar panel is likely going to get dusty. Depending on how remote this system is, you may need to clean it off once in a while. Worth calculating how much runtime you can get when only recording in set windows and in a low-power listening mode for the remainder of the system's on-time. Depending on constraints, fitting the system with a battery bank and not relying on solar could be a valid alternative.
25 January 2025 1:06pm
Not exactly an answer to your question, but I'm not sure if it would be worth it to combine audiomoths with a solar panel, since if the battery power isn't the limiting factor for deployment time, the sd card storage will be. If you have to replace or empty the sd cards every now and then, might as well replace the batteries right?
Or am i overseeing something?
Carly Batist