I was planning on creating a watch capable of producing around 125 dbs of sound for self defense: it would irritate/incapacitate an attacker and possibly give the victim an opportunity to leave the scene. Is 125 dbs of sound capable of causing irritation in attacker(s)? If not, then what intensity of sound is required? If yes, then how long does it take to affect the attacker?

My requirement is that the sound should affect the attacker within 5-10 seconds.

The victim would be wearing protective headphones for noise cancelling.

  • $\begingroup$ What exactly do you mean by irritating? Disorient, annoy, slow down, ...? Also, this might help: decibelcar.com/menugeneric/87.html $\endgroup$
    – Soan
    Commented May 27, 2019 at 12:12
  • $\begingroup$ Disorient of possible or annoy enough to make attacker avoid the victim. By the way thanks for the link :). $\endgroup$
    – Mehawk
    Commented May 27, 2019 at 13:47
  • $\begingroup$ How are you directing the noise toward the attacker? If the watch is simply spewing 125db of sound, it's as annoying/dangerous to the wearer as it is to the attacker. $\endgroup$
    – JBH
    Commented May 27, 2019 at 14:13
  • 1
    $\begingroup$ An extremely loud sound, if it has any effect at all, will also affect the victim. You can teach someone a few very basic self defense moves that almost anyone can use to do this, and teach them in a matter of half an hour. $\endgroup$ Commented May 27, 2019 at 14:57
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    $\begingroup$ Your title is about causing death. Your body of text is about causing irritation. Pick one! Is it about death, irritation, or something inbetween (ear pain or damage)? $\endgroup$
    – Cyn
    Commented May 27, 2019 at 19:49

1 Answer 1


Can a sound of 125dbs from a watch be used lethally for self defense?

Lethally? No.

Is 125dbs of sound capable to create irritation in attacker(s)?

You haven't defined "irritation", but it will be annoying. You are, however, aiming waaaay to low... the human threshold of pain for noise can be as high as 140Db.

There are already cheap, off-the-shelf commercial products which claim outputs of 140dB. Here's one example (commercial link. I have no relationship to vendor). There are plenty of webpages out there discussing use of rape alarms... this one suggests that you'll want at least 130dB, and you use it to "shock and disorientate" your attacker. It'll work almost instantly as it will cause immediate physical pain.

Given that these things are not particularly expensive or hard to come by, you may find that the best bit of research you can do on this is to buy one and set it off yourself. It'll also give you some appreciation for the effect this device will have on the user as well as the target.

If no, then how much dbs is required?

To kill someone? Sperm whale sonar might do; that's 200dB+. Given the logarithmic nature of decibels, I'm sure you can see that this is a lot more powerful that your theoretical device.

To "stun" someone is a bit easier, especially as there are commercial and military devices out there to do this, too. A stun grenade (or flashbang) might hit 170dB, and that'll certainly slow down anyone who finds themselves in close proximity to it.

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    $\begingroup$ ... "200 dB": at 194 dB the sound pressure is 1 atm; anything more than that is not "sound" as such (because obviously you cannot have a harmonic wave with an amplitude larger than 1 atm), but rather a shock wave. $\endgroup$
    – AlexP
    Commented May 27, 2019 at 12:43
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    $\begingroup$ @AlexP this is true, though the person on the receiving end of a suprise 200dB shockwave will be in no state to point out the inaccuracy, and you'll be able to run quite a long way before they can find a supporting reference. $\endgroup$ Commented May 27, 2019 at 12:45
  • $\begingroup$ @Starfish Prime Thanks for the answer. Since threshold of pain is 140dbs as u told....I don't think 130dbs can cause almost instant pain. So, It seems for that I must go for above 140dbs. $\endgroup$
    – Mehawk
    Commented May 27, 2019 at 13:45
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    $\begingroup$ @AlexP 200dB would be impossible as a "sound wave" in the atmosphere, but Sperm whales operate underwater. The thresholds are different there. $\endgroup$
    – Cort Ammon
    Commented May 27, 2019 at 17:28
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    $\begingroup$ @CortAmmon the risk of underwater rapists is lower for humans, but it isn't clear what the purpose of the OP's device is. $\endgroup$ Commented May 27, 2019 at 18:44

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