I had a very similar experience. Here in racine, wi on tuesday we had a very bad storm. The thunder sounded exactly like sheet metal sound effects from an old Movie. I have never heard thunder like this in the 28 years I have lived here. At its peak the thunder lasted well over a minute without stopping. It was one continuous rumble.

Interesting. There have been reports from Tennessee and Arkansas with similar things taking place. Crackling dirt, or rocks, when they are driven over, but very loud and deep sounding, coming from the air. And then sounds like large boulders cracking. All of this reminds me of the book and movie the "langoliers". Around the same time there was EQs in both areas, and People could feel the swaying motion, felt dizzy, etc. So maybe its related to the EQ activity somehow is Cali as well? Dont know, but very interesting indeed.

I currently reside and Arkansas. I have heard this same sound during recent thunderstorms as well. I to was awoken one night to one of the loudest sounding thunder I Have ever heard, it literally rattled my home and had my dogs barking for 5 minutes.

The locals have been talking about the military doing some interesting stuff in the sky. From what I have heard they are performing experiments while they fly and are masking it with a white gaseous substance that dissociates into the air rather quickly. I think this "testing" has something to do with what ever they are doing up there. I actually caught two pictures of what the people have seen around here on my iphone. I will upload them in the morning, as I am extremely tired, but what I saw was pretty amazing. First, I saw a white lines popping out of the air, they were moving like a plane was dropping them, but no plane. Almost like they were painting the middle lines in a road up in the air. After a few minutes they immediately began to look like a small cloud, and then vanish.

We have also had an unusual amount of earthquakes in my area with one hitting 4.4, which was felt by many in my hometown.

Something strange is indeed going on

Hello this is my second time posting in ATS. My first time I was jumping into someones thread about seeing moving stars that zig zag in all directions....Any who.... I read this thread when it was first posted and started to think to myself "Damn I want to hear this for myself" But yesterday night there was a rain storm....No lightning or Thunder at all just rain.....and I heard this noise like something was hovering in the sky...and the noise it made...It literally sounded as if something was above sitting there..It was going on for a long time too. I remember earlier in this post they said it sounds like gears moving....To me it didn't really sound like gears that we are used to hearing....but it could of past for gears with a Hydrolic System.......I asked my wife if she heard the noise ...Instantly she said I was crazy but a few seconds later she heard it too. It did sound kinda like that video (minus the static noise) but much more clear and there were some loud Booms too maybe 2-3 of them and they didn't sound like thunder at all....It's more like if something exploded like a firework. Now let me tell you my location of where I live. I live on top of a hill where I can for see 30% my town and behind my house I can see onto Revere Beach from a distance. Planes usually go around my directions certain times of the day but you can hardly hear them sometimes and planes don't make a sound like I heard last night. The sound lasted too long. I also live 3-4 miles away from GE Aviation. This is where they test Plane engines and out of my 3 years living where I am today I only heard the testing once and that was April in 2008. I know this wasn't the sound because I could hear the testing from the distance where it was coming from and it lasted for 24 Hours shaking my bedroom wall that was facing in that direction. So none of these could be what I experienced before and this is all new to me.....I was more interested in it last night because of this post i read... The noise went on for a long time ...Stopped for a minute and it proceeded to make more noise. I don't know what IT is but I'm going to be listening more often now.

Where at in los angeles?

From the countless youtube video's of this particular day (Oct 19, 2010) there were 2 different systems of storms, one during the day at places like Irvine, and one at night in places like Palmdale and Hesperia. None of the video's I watched were from Los angeles, and the thunder sounded normal in those videos too, I think.

Was it night at the time?

This was around 1pm in Newhall, CA

No clouds in sky at the time, I inspected it looking for a hovering plane or helicopter.

Was the sky clear or storming at the time, 5 days later?