It seems to me that I’m more likely to hear a blimp or any distant aircraft for that matter, if I’m down wind of it. If I’m upwind or there’s a crosswind, not as much.
Is it me or some sort of confirmation bias thing?
Just remember, folks: it’s not the noise of a blimp that should strike you with horror
(link is to one of the classic, funniest threads in the history of the Dope. How did we get to 20 posts without mentioning it?)
Well, it would be more accurate to say I hear a blimp before I look for it.
Ignoring small toys & hobby craft under a few kilos weight …
There are a few research or record-setting aircraft which use electric motors. Most (all?) are unmanned. The typical goal is solar-powered high altitude long duration flight as a sort of on-call low cost satellite for observation or communications purposes.
There are AFAIK no production models of electric motor powered mainstream aircraft of any kind.
I recall a couple of efforts in the last 2-5 years to build a light trainer aircraft using a powertrain similar to a Prius: batteries plus an IC engine turning a generator provide electricity to an electric motor which drives the propeller. I think they got their prototype flying, but were still suffering from the batteries’ low power/weight and power/volume ratios. Plus the inherent inefficiencies of converting fuel -> heat -> motion -> electricity -> chemistry -> electricity -> motion.
Sorry no cites for all the above; I read a lot of stuff on topic but don’t bother to retain the names of the companies or projects, so I have no good Googling hooks.
Airbus is working on a pure electric airplane powered solely by batteries: Airbus E-Fan - Wikipedia
I keep thinking this should be about the noise a blimp would make if it popped like a balloon…
I used to have a tall tree used as roost by a large flock of small birds. Every evening as the flock settled in, it was quite noisy. One evening they all stopped at once. It was so striking that I went to investigate.
A 1000 feet up was a blimp heading in to Moffett Field. Too quiet for me to hear but I guess they thought it was a large hawk.
I happened to be at Hanscom field just outside of Boston when the Hood blimp came in for a landing. As others noted, it is not silent at all. It sounds roughly like a couple of small planes doing engine checks on the ramp. That is to say, it is fairly loud if you are close to it but not especially loud once you are away any significant distance. It is just a loud buzz.
What is fun to see is how they land those things. It is positively low tech. They drop ropes off the side, the pilot tries to go for neutral buoyancy and then a pre-staged ground crew grabs the ropes and physically pulls it down the last few feet and ties it to the ground. I hear that strategy can be pretty harrowing if there is any wind at all. The landing I witnessed required about 12 large men grab the ropes and pull it down.
I was outside today when one of the loach helicopters was stringing up a wire. I’ve decided that at a distance, blimps and loaches sound the same (a droning noise). When a loach is as low as a blimp, it is louder. I am assuming a blimp cruises lower than a helicopter, but I am not sure.
Interesting about the Cessna/Piper engines, because that’s just what a blimp sounds like to me. Some years ago I had a chance to go up in a fair-sized blimp. I don’t remember its size exactly but the gondola was large enough for maybe eight or ten people, plus two pilots. Anyway, while waiting on the ground and the thing was buzzing around, it sounded a lot like a small Cessna at cruise, not loud at all. Certainly not at all like any helicopter I’ve ever heard, which have all been obnoxiously loud. In fact sometimes one of those helicopter air ambulances flies overhead not far from the house and the loud thrumming sound comes through distinctly even with all the windows closed. If a blimp went by under those conditions I wouldn’t even hear it. (Around here, the air ambulances would more likely be the AgustaWestland AW139s rather than the Sikorsky S-76s also in the fleet; they are about the same size.)
I don’t particularly remember how loud the blimp was from inside the gondola, so it must have been fairly low to moderate. I remember noting with interest that the cockpit looked almost exactly like that of a small airplane, which seemed to give a deceptive sense of control because, after all, this wasn’t an airplane at all but a friggin’ balloon – which just happened to have some engines attached to help it move around a bit!
Just had to confess this (after about at least 35 years)…
I had been at some friend’s house on the south side of Chicago having a few drinks, maybe smoking something. I’m driving well after dark up the Outer Drive. (For those who don’t know, the drive runs along the lake for over 20 miles. When you’re on the south side heading north, you get a great view of downtown Chicago - all the beautiful buildings lighted up, etc. - as you drive toward it. To your right, the lake at night, is pitch black, of course.) At some point, something catches my eye and I look up over downtown, and I see a light. Often, planes fly over the city on their way to land at one of our then three airports and seeing the lights of a plane wouldn’t be unusual. But they move. This one didn’t. And this light blinked out. I freaked. Then, as I watched, the light came back and even grew larger. And then, as I watched, it went dark again. I knew I was a little buzzed but I also knew that although it couldn’t actually be a UFO, I had no idea what it was. I thought that maybe it actually was a UFO. I know it couldn’t be, but I wondered just the same, could this be IT?? I was really excited. I couldn’t pull over and I was having a hell of a time driving and watching at the same time. Several more times the light changed. It began to get more clear to me and I could see that the light was a horizontal bar that started as a dot, lengthened, and then either got smaller again or blinked out. By this time, I was half-way downtown and totally amazed. It seemed to barely move, as if floating over the city, and I knew it couldn’t be a plane. I wondered if anyone else in the city was seeing this apparition/UFO/bizarre unknown light in the sky. As I got closer, it started to become apparent what I was seeing and I had to laugh. It was the Goodyear blimp. That blimp has a lighted sign on the side that has a running crawl of words. A sentence begins to appear on the left, works across the side of the blimp, and then disappears off to the right. Or it just goes dark. When I got to the point that I was about underneath it, I opened the window and could hear the buzz of the motors. I’m a professional skeptic and I’ve never told anyone that I thought I saw a UFO. At least for a few minutes I actually wondered if that’s what I was seeing. Funny and embarrassing at the same time. Even now.
Everybody’s seen a UFO. Sometimes you get an explanation later and sometimes you don’t. It doesn’t mean anything more than U=Unidentified, not Alien.
I had an experience almost exactly like yours. My wide and I were part of a crowd coming out of a movie theater, at least 30 years ago. People stopped dead in the parking lot and started pointing up at lights in the night sky. They moved weirdly and no sounds of a plane could be heard.
Fortunately, the next day the newspaper ran an article about the UFO that so many people had reported. I don’t think it was a blimp, but some other aircraft with an advertising sign. From our distance the rest of the craft was invisible; only the floating lights remained.
Seeing a UFO has nothing to do with being a skeptic. Believing that there’s a natural explanation, even if one isn’t handed to you, does.
We had a blimp fly right overhead one time. And I mean directly over our heads. It was a small one. I have no idea how high it was, but it looked low. We didn’t hear a sound. Our dogs might have; they certainly barked at it, but they were also looking up at it so I’m pretty sure they saw it.
It was spooky weird.
I’m gonna bet the words appear on the right and scroll to the left. They’re very hard to read if presented backwards. 
I saw my first UFO about 4 years ago. I had just walked out of a restaurant into a foggy night with a light drizzle falling. And there in the dark sky out beyond the parking lot was a strange blue-white light in an odd shape, just hanging there.
I stopped and stared for a few seconds and couldn’t really figure out what it was. I had that same strange sensation of “This *can’t *be something unusual, but at the same time, what the heck is it?”
I was beginning to lose faith that it was something ordinary, convincing myself it was something weird, remarkable, maybe even dangerous. Then suddenly it hit me.
It was a parking lot light. One of a dozen identical lights on tall poles in the lot. There was a gap in the housing so some light was leaking out the top in addition to the usual downward illumination. And the housing was square and close enough that the bright area was clearly rectangular, not just a point. It was all of 150 feet away.
I’d walked out of that restaurant dozens of times, usually after dark. And seen that light post and fixture each of those dozens of times. But somehow the fog hid the post and fuzzed up the shape enough to make the whole thing real mysterious.
I’ve spent a life and a career looking at the sky from many vantage points. And I finally get fooled by a stupid light post in a familiar parking lot.
Human perception is a funny and fallible thing.
As a kid (prob. 3-4 years old), me, my dad, a friend of mine, and his dad got to take a ride in the Goodyear Blimp ‘America’ back when they were based out of Spring, TX. (there’s a Lowe’s where the hangar used to be) now.
Anyway, they weren’t terribly loud from outside, unless you were up close, but they were really pretty loud inside.
I was thinking more of a satisfying boing sound as they bumped into something.
Years ago Calgary used to a very active ballooning culture. At one point multiple craft were visible about the city daily. Not just the standard colourful stuff which was great to have in itself but elaborate shapes, there was a Bart Simpson, Godzilla, and a blimp. The blimp was quiet, but you could certainly hear it. Often enough you heard it before you saw it due to buildings obscuring the view