Changes in thunder

[Dave Gallaher]

I'm sitting and listening to the welcome sounds of thunder as this system works through the area. From my unscientific observations (utilizing a musical ear), the sounds made by thunder differ depending upon whether the discharge is cloud to cloud or cloud to ground. CC bolts, even those fairly close to the observer, offer the familiar crackle and crash, while those bolts that come to the ground seem to add a huge low-frequency component to that sound.

Are there any published studies involving this? Or am I wrong in my observations? Just wondering...

 

[Richard Dickson]

Dave,
I don't know about published studies, but I agree that there are a multitude of different sounds associated with thunder. The one's that I enjoy the most are the 'Super-bolts' where the low pitched strong thunder takes forever to go from one horizon to the other. That's just nothing short of erotic!!!

 

[Mark Ellinwood]

I have also learned how to differ between IC and CG lightning depending on the resulting thunder... CG is typically crisper, with a more staccato sound, where IC is typically dull and drawn-out more.

 

[Richard Dickson]

The subject perked up my curiosity a little more. At the moment this is the best information I can find about the sounds of thunder. I'm hoping someone can come up with something better.

www.weatherscapes.com/techniques.php?cat=lightning&page=thunder

It is also worth your time to explore the rest of this website as there are some very good photos of different weather phenomena.

 

[Adam Lucio]

I can tell the kind of lightning by the thunder too. I haven't read any studies but if you understand the basic principle behind thunder which is air expanding after being heated by the strike...then the kind of lightning strike and its relation to thunder makes more sense.

A super intense, "hotter" positive CG strike would have the deafening explosion sound...whereas an AC lightning bolt that is "cooler" and can span the entire horizon would produce a longer, duller rumble. Distance from the lightning would also come into play.

Thats how it always worked out in my not-so-scientific mind.

 

[Dave Gallaher]

I've been under some VERY loud CC bolts, with only 3-6 seconds or so between flash and sound. In my experience, the volume with these can be about equal to a CG.

Forgive my musical references here, but I don't know how else to describe what I perceive as the difference. Both CC and CG make strong presentations in the treble range, the crackle and pop, along with a big midrange crash. Both can be heard and physically sensed on the body as what I assume is the shock wave reaches the observer.

The difference I hear is when a bolt comes to the ground, it's like hooking a subwoofer to a sound system: the low-frequency booming sound is huge and carries its power over a longer distance. Just as when one approaches a musical venue from down the street, the first thing heard is bass and kick drum--the lower frequencies resonate the walls and carry for some distance. The low frequency thunder gives one that punched-in-the-chest sensation, and I've only observed that on cloud to ground strikes.

 

[Glenn Rivers]

Sound of Thunder

I think that Dave is spot-on about the differences between CC and CG thunder. That reference about adding a subwoofer to the spectrum of frequency when the source is a CG flash is an excellent analogy.

Just as for Dave, I sometimes think that I can distinguish CG from CC thunder by the presence or absence of that low frequency thump that only seems to occur with CG events.

A puzzling type of thunder that I have heard on rare occasions consists of thunders that do not have a hiss or crackle preceding the loud thump of "normal" CG thunder by a second or two. These thunders have only the loud whump with no mid range or higher frequency sounds. In these events, the low frequency sound seems enhanced and can almost seem foundation shaking.

Could this type of event be very high amperage positive CG lightning from the anvil of a storm that is mostly producing more numerous negative CG's that most storms around here (Ontario) produce, along with the more typical sounding CG thunder?

I remember experiencing several of these weird ground shaking events over a period of about an hour or so during a steady light to moderate rain from a parallel stratiform region of a training MCS. The heavy convective downpours were about 20 miles away from me and the more frequent CG's that were probably occurring in and around the updraft-downdraft couplets were too far away to hear.

 

[Willoughby Owen]

If there's one thing I've noticed in the noise of thunder is how it differentiates between latitude. The thing that strikes me the most since living a fair way into the tropics (latitude -12S) is how deep the thunder sounds compared to the cold-air thunderstorms I often got whilst in New Zealand during winter/early spring which "crack" more and sound more "tinny".. but this could be just because the cloud tops are no where near as high than here in Darwin, ~33kft compared to 60+kft.

From how far away can you guys hear thunder from a distant cell? You can hear them quite easily from 70km (43.5 miles) away if the skies are clear and you can see that cell.

 

[Kurt Hulst]

I know the time of the year has a barring on thunder. Thunder seems to be more booming and sustaining in the winter months, in the states, because of the lack of foliage. There's less to absorb the sound.


I also notice a difference in location. Here in Michigan we have lots of trees and in the summer thunder can seem more muffled than if I were observing a storm in the plains.

I have chased many supercells. one in particular June 26, 2005 in SD. Its thunder was very booming. Scott Olson and I were trying to get out of the barrage of lightning. As we were doing so every bolt was like a canon very sharp and deep. It was like we were dodging mortar fire.



If you really want to know about this observation ask Dan Robinson.

 

[Jason Foster]

Kurt, you probably hit the most probable reason for difference in the variety of sounds thunder can make.....attenuation.

Trees, mountains, hills, buildings, storms, snow, etc. all can act as either a baffle, a reflector or even a refraction of the sound waves.

While the other reasons discussed (temp. of strike, length of travel, speed of travel, etc.) are correct also, I think most of the perceived differences start with the environment which the observation is taking place.

I have always notice a big difference in thunder sounds from my observations here in the Mid-Atlantic to those on the plains. similar to the plains, but still with it's own unique character is thunder in the everglades of Florida, and even those I've observed in the middle of the Florida Keys (that is something you've got to experience!!).

Trees have been one factor I noticed makes a difference in this region. Some seasons when we get a thunderstorm in March before the leaves come out, the lightning strikes produce thunder that is more closely (but not nearly the same as) the thunder in the plains. The sound waves are likely less attenuated because of the lack of baffling from the dense leaves we have. Interestingly, since there are more tall parking garages in the area now, I can monitor storms above the tree line and this is one way I started to notice the difference.

The storm itself is also a factor in that I suspect many of you have already noticed the difference with HP storms versus LP. Particular memories of LP storms, especially when there is a good wall cloud present, the lightning tends to have that deeper base frequency easily to the point that I can feel it in my chest.

I don't think there is any real scientific bearing on the importance of the various kinds of sounds thunder make, but it certainly would be very fascinating to see the wave forms of very high quality recordings.

 

[Mike Kovalchick]

I thing I've noticed is that Winter thunderstorms..in particular those associated with snow, sleet or graupel seem to have a much higher percent of positive strokes associated with them. Positive strokes..having something like 10 times the power of a negative strokes...sounds more akin to dynamite or a detonation rather your typical thunder sound.

I think that is yet another factor that adds to the different sound characteristics found from Winter storms.

 

[Jason Harris]

This doesn't get into detail about the types of sounds, but the analysis does acknowledge the role of humidity, temp. etc. when it comes to the perceptionhttp://www.lightningsafety.com/nlsi_info/thunder2.html:

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Sound velocity is proportional to the square root of temperature. Temperature typically decreases with height, unless there is an inversion (warm air over cooler air). Thus, the sound of thunder will be deflected upward. Humidity, wind velocity, wind shear, temperature inversions, terrain features, and clouds, also influence thunder's audibility. The loudness of thunder can be expressed in decibels (dB). A clap of thunder typically registers at about 120 dB in close proximity to the ground stroke. This is 10 times louder than a garbage truck or pneumatic jackhammer drill. By comparison, sitting in front of speakers at a rock concert can expose you to a continuous 120+ dB level. Thunder in close proximity is capable of producing temporary deafness and may cause rupturing of the ear's tympanic membrane that can lead to hearing damage or deafness.

At very close range, thunder is capable of causing property damage. The shock wave, pressure, and propagation of thunder may cause exterior and interior damage to structures. Popping of nail-supported drywall away from horizontal and vertical wooden studs inside houses has been documented. Glass windows have been broken by the concussion of thunder.

This is interesting also:

If you have had a lightning bolt crash down really close to you, the thunder doesn’t rumble as much and sounds more like an explosion. That’s because the compression waves didn’t have a chance to bounce off many things before you heard it. Whereas if you were further away, you would of heard the rumbling.

http://www.weatherimagery.com/blog/facts-about-thunder/

Stated comparably here too in terms of diffraction:

The thunder from a close bolt of lightning will be experienced as a sharp crack, indicating the presence of a lot of high frequency sound. The thunder from a distant strike will be experienced as a low rumble since it is the long wavelengths which can bend around obstacles to get to you. There are other factors such as the higher air absorption of high frequencies involved, but diffraction plays a part in the experience.

http://hyperphysics.phy-astr.gsu.edu/hbase/sound/diffrac.html

 

[David Shohami]

I must share this recording I made of a thunder from a CG lightning hitting <20 meters from me. I recorded this near Washington DC in August 1998.

The thunder I'm referring to starts about 17 seconds into the recording (the previous thunders are all more distant rumblings).

What amazes me in this recording is the sound of something which I always thought to be like a whip just before the explosion comes. Pay close attention and listen with headphones! I've never experienced anything like this sound since (perhaps I haven't been as close to a bolt since), and I wonder what caused it.

Change the file extension to mp3 before playing (this is NOT a powerpoint file!):
http://img2.timg.co.il/forums/1_136812820.ppt

 

[Dan Nichols]

"Downhill" Thunder

There's a sound to some thunder that I'm not too crazy about when I hear it. It is a somewhat hollow sound that has a definite tuned tone or note. To all you musicians or music fans, it is like the sound of tuned tympani (or kettle drum) in a symphony orchestra. It usually means either that the storm max has just passed, the storm itself is dissapating, or the storm is "going around you" as I've much too often experienced. I suspect it is a CC that is way up in the clouds. When heard at the onset of the storm, it usually means dissipation unless a new surge of energy develops nearby.

I have heard that whip-like TICK actually up to one second before the loud thunder report. Not necessarily loud in itself, but the following thunder usually is.