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I was caught in an electric storm last night while camping. The time between flash and thunder must have been 3 seconds or less at least five times. (The nearest hill peak which could have been attracting the lightning, was about 160m higher than me and 600m away.) I found it quite scary, and found myself hoping very strongly that it would not strike anything closer than that hill peak 600m away. When that close it sounds like a like a bang, series of bangs, or a prolonged ripping sound. I covered my ears to protect them, it was that loud.

How close does a lightning strike have to be to be perceived at 140dBP (dB Peak Pressure), which is a level of noise which is unsafe for any period of time? (I would also be interested to know of any data on the greatest possible distance from a lightning strike for injuries other than permanent hearing loss, eg from debris flying out from the strike, but that is secondary.)

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That's an unanswerable question. Lightning and thunder vary all over the place and even "how close" is difficult to define since lighting is a spatially distributed and doesn't happen at a single point.

This being said: Hearing damage through lightning is a very small risk. While it's loud, it's also very short.

Case in point: Roy Sullivan (https://en.wikipedia.org/wiki/Roy_Sullivan) was hit 7 times by lightning and there are no reports of associated hearing problems.

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  • $\begingroup$ Well, in my situation the risk was higher. If there has been no nearby hill peak and the lightning had hit randomly in the circle of radius 1km from me, there would have been a 5% chance that one of these 5 strikes would hit just 100m away from me. I don't believe the centre of the bolt needs to hit you to injure you (only one of the probe bolts), but I'd imagine the most likely injury when more than 30m away would be a hearing injury (which would be nice to verify/quantify). Wikipedia says it's 165-180dB "near the source", maybe this provides a lead? en.wikipedia.org/wiki/Thunder $\endgroup$
    – novice
    Jun 25 at 12:32
  • $\begingroup$ It says here: ncbi.nlm.nih.gov/books/NBK441920 "Many victims struck by lightning will also have an injury to the audio-vestibular system due to either blast trauma or electrical injury. A ruptured tympanic membrane is common and found in 50-80% of those struck by lightning." Hearing damage due to lightning strikes is also mentioned a few times in this Wikipedia article: en.wikipedia.org/wiki/Lightning_injury; also at en.wikipedia.org/wiki/Thunder#Consequences: "Thunder can rupture the eardrums of people nearby" $\endgroup$
    – novice
    Jun 25 at 13:49
  • $\begingroup$ @novice as you can see Wikipedia says "near the source" without actually quantifying it. Hilmar is very right in their answer stating that quantifying the distance would actually be kind of impossible without more knowledge on the source. First of all the source is spatially distributed and even "worse", its dimensions are way larger than the distance we are talking about and this makes the inverse square law obsolete in this case. You would have to resort to other methods to calculate the pressure at a specified distance, leaving out the reflections from ground etc. All of those (cont.) $\endgroup$
    – ZaellixA
    Jun 27 at 13:54
  • $\begingroup$ (cont.ed) methods require knowledge of the amplitude (be it velocity, voltage, pressure or the quantity of interest on the surface of the source interfacing with the surrounding medium) distribution on the surface of the source. It is rather difficult to acquire such knowledge even more when it comes to highly non-linear phenomena with large deviation from realisation to realisation $\endgroup$
    – ZaellixA
    Jun 27 at 13:56

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