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Comment by quickthrower2 | Hacker News Reader

The highest decibel things my kids are exposed to is themselves.

I have loud children, but they don't actually reach 110dB. I mean, YMMV, but I'd notice if there was something literally as loud as a rock concern in my basement or backyard.

Sure they do. I did a quick search and 110-130dB comes up on every result.

It's all about where you measure from, due to the inverse square law. For measuring things such as speakers for product specs, the standard is to measure from one meter away. But for rock concerts and hand dryers, you measure from the typical listening position.

I think you are considering your typical listening position for your child differently from the search results I found. If you were giving your kid a kiss goodnight and they screamed, it would be louder than if you were in the audience of a rock concert (but not louder than if you were kissing the concert speakers).

Every time you double the distance between the source and the meter, the meter reads 6dB lower.

Minor factoid: While that’s true in the limiting case (far away) for rock concerts, it’s common to use line arrays which fall -3 dB when you double your distance, as long as you’re within a certain range. Within this range they follow inverse rather than inverse square.

Is that a similar effect to antenna arrays?

It is most similar to the effect of electrostatic charges. The effect of a point charge is the inverse square of distance, the effect of a line charge is the inverse of distance, and the effect of an infinite plane has no relation to distance.

Ok thanks that is a useful mental model

It's more similar to an antenna that isn't an array. But you could compare an antenna array to a microphone array, sure. They both work by tweaking the phase and relative gain to arbitrarily change directivity without a need for physical directivity techniques. Like how home voice assistants and multi-antenna wifi APs achieve long distance reception without also amplifying 360 degrees of noise. They do a thing not unlike camera autofocus in that they quickly home in on whatever optimizes s/n.

Very true. Most other things are approximately point sources, and even then it's unpredictable until you're at a sufficiently far field. And then there's free space, half-space (as with a wall mounted dryer), etc.

There’s also the tensor tympani muscle. I would assume that children tense it when shouting at full volume, which will somewhat reduce the effect.

That mitigates self-screaming, but not partner-screaming.

You're right. I should have specified that they don't put out the power of a rock concert.

Or one of these dryers, for that matter.

They are loud, but not as loud as one of these devices; not even close.

No worries, I know that's what you meant, and the point is that the power/intensity/volume/etc. at the source location really doesn't matter for this: at the listening position is what matters.

You're very likely some minimum distance from the speakers and from the dryer, but the minimum distance from your child could be nil (as in the 130dB claims) or significant (as in your experience), making it really hard to use something like a child in this conversation.

Yeah, no joke. Kids shouting in your ear can cause permanent damage. I have a friend whose kid did that to them, and they now have problems hearing with that ear.

Mine did. My wife has permanent hearing loss from my daughter screaming in her ear. Years later she still says the best Mother’s Day present I ever gave her was a pair of gun mufflers.

can confirm this to be true

And I can corroborate.

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