This was a little audio amp from Radio Shack.
This little amp has an input capacitor, so you can hook it directly to DC of a solar panel.
I turned the gain up all the way and
connected the amp to the output of any selected solar panels. I had previously
established the capability of isolating any panel with switches.
Now, not only can any panel be isolated for measurements and performance,
but also for noise and audio.
I was hoping to hear solar noise from the sun, or shooting stars, or blinking airplane lights.
I could only hear two things:
One was the noise of the controller. Quite irritating!
And this is the reason for the 4700uF capacitor.
The solution worked well. That basically ended the noise, and probable increased
the efficiency of the solar panels.
The second thing that I have heard are artificial lighting 60 Hz hum, found in
parking lots. And it is so loud that I have to turn off the amp.
And this applies to the yellow sodium lights as well as florescent lights from store windows.
And it does not have to be night time either. Those lights are loud, day or night.
I have not heard any shooting stars or lightning flashes!
But I do not know when to listen either.
So it may work after all, and I have not witnessed it yet.
After several months of listening, I now have heard flies and bees. Quite unexpected!
Every time I hear bees, I climb to the top of the roof and see absolutely no bees.
Then I realized they are in tree limbs above, 15 feet away.
And it is definitely bees in flight as
you can also hear the doppler shift as they fly toward or away.
Also, I "hear" flies. Flies are much loader, give only a single pass, and have a distinctive doppler and buzz
that is a "fly". The acoustic signature in light from a solar pannel sounds identical to what you would hear from the acoustics in air.
Also can hear at times what I describe as nats or mosquitoes in a swarm. I have not
identified this noise yet. It has musical qualities. It is high frequency: about 5khz.
But some nat swarms are almost impossible to see: They can be high in the sky, and you have
to know they are there before you know where to focus. The human eye can not "see"
5 khz at all. Vision is limited to only about 60hz.
This strange sound can be rendered to sound and consequently heard
but the original identity is masked. At least for me. I have no idea!
The one and only time that I heard this sound was at a lake.
And there were rain drops on the solar cells. I know that the cells were seeing horizontally
through these rain drops.
To further investigate these strange sounds,
I purchased a small 6 volt solar cell from RadioShack, and an additional amp.
The large solar panels on the roof can not be pointed at any one target.
A small portable version is the
only way to see where these sounds are coming from.
I have verified the bees, flys, and other flying insects with this little setup.
Ofcourse, I have to be about 3 feet away to hear these things.
The big solar panels on the roof have such huge gain,
that they can hear a bug over 20 feet away.
I have found that solar cells produce strange sounds from internal resistance as the cell
heats up or cools down. I can identify them, as they are usually below one hertz.
And produce a "waving sound" or "pulsation" in the white noise.
The white noise will wax and wane at an audible rates. The white noise is modulated,
and produces rapidly changing frequencies, even up into the audible range.
At first, I thought these sounds were waves or ripples in the upper atmosphere.
With two different densities of air layers, waves could exist in theory.
And it would be highly unlikely that I would have discovered something that no one else
But I have isolated it down to the cells themselves.
Here is another phenomenon:
If I am behind or in front of a automobile, I can usually tell if they have LED taillights or
blue headlights. I can hear alternator whine.
All incandescent have slow reacting filaments and are silent, and this corresponds to
about 90% of the cars on the road.
If I am to the side of a car, I can hear the hubcaps if they are shiny and if they are moving.
Solar cells can hear the wind! This is amazing. If the wind is blowing in tree limbs
that have no leaves, you can hear the wind. The small twigs are vibrating and reflecting
sun light. The sound is identical to the acoustic sound of wind,
and is immediately identifiable to the human ear.
And it is louder inside the RV through the speaker, than outside.
Some trees are louder than others, and some make it sound as if a hurricane is outside.
I did not know the frequency response of a solar cell.
After all, my investigation could be hampered if the cell has restrictions on its response.
Here is a way to tell approximately:
By using feedback!
Reflect sun light off of a surface that will vibrate. Here I am using
a tea bottle.
(It is not positioned correctly in the picture.)
Aim the solar cell at a reflection from the tea bottle,
and have the amp positioned near the tea bottle too.
Feedback reflections work great, and are very sensitive.
The cell will pick up a change in the light, and cause the amp to produce a sound, and the sound will be felt by the
side of the bottle. Oscillations instantly build up to produce a high pitched frequency.
The loud squeals are ear piercing, and sent my dogs running for cover. So be prepared:
It will hurt your ears.
By changing the positions and such, the highest frequency that
can be manuevered is about 10 kHz.
But this tea bottle is only a crude setup.
Cells may go to several hundred kilohertz, as far as I know. And I don't know.
What I do know from this tea bottle is that they can go to at least 10khz.
You should be able to hear music playing inside automobiles if you can catch a reflection
from window glass. I have not heard this yet...