I would guess that they use more expensive hearing protection systems with an active electronic system to pass through sounds at a comfortable level, attenuate louder and potentially damaging noises, and possibly even amplify quiet sounds.

The technology would be similar to that used in hearing aids and noise-cancelling headphones. But it is also probably an order of magnitude or two more expensive just because the primary customers are tax-funded.

Without electronics, I could also conceive of an earplug with a winding channel bored through it, past flaps that can block the channel by moving too far in either direction and forming a seal with the outer wall of the channel. Sound energy above a certain level would push the flaps closed as the air vibrated, and would thus attenuate louder sounds to a greater extent than quieter ones. If the flaps were tuned to different sound energies, the loudest sounds would push closed the most flaps.

That would require some precise machining to fit inside the outer ear canal. The electronic filter might actually be cheaper.

Usually the ear protection used just has a simple narrow channel. This is effective in attenuating loud sounds without impacting quieter sounds as much. The name brand I'm most familiar with are the SureFire Sonic Defenders. They're in-ear, not very visible without the retention cord attached unless you're specifically looking for them.

You can get a basic set of electronic ear pro for ~$70 (http://amzn.com/B007BGSI5U), there are even cheaper options with a lower NRR.

Those look a bit bulky for use by police or military in the field. You would need to miniaturize down to an in-ear version. Then you need to add very generous padding in your procurement contract.

If an over-the-ear tech is available for civilians for $70, I would guess that an in-ear police/military version is $850, with an upsell option to integrate with your existing radio communications system for only $1150 per pair. I'd also call it "active hearing protection system" and never, ever refer to them as "earplugs".

That's comparable with a good hearing aid, only because the health insurance payments system is superficially similar to government procurement contracting with respect to profiteering middlemen.

Again, this is only a guess, made without supporting data by someone who owns a foil hat.

These seem to be more along the lines of what is issued:

http://archive.armytimes.com/article/20090908/NEWS/909080313...

> Soldiers can adjust the rocker with a quick "click" depending on the amount of protection they need. When it's in the open or "weapons fire" position, sound can travel through the sound channel filter into the ear.

> For noisy environments that don't require an acute listening capability, such as around helicopters, troop carriers or generators, the rocker can be switched to the closed or "constant protection" position.

There's also larger over-ear kinds that are integrated with comms:

http://www.bosssafety.com/p-10356-peltor-comtac-iii-a-c-h-he...

This style has both active and passive configurations.

For those hitting the paywall on the the first link, the in-ear protection resembles 3M Ultrafit earplugs, with a hole bored through the center. The rocker switch may be lengthening or diverting the pass-through channel, like the rotary valves on a tuba or French horn. A longer or narrower channel would provide more attenuation of all sounds. It may also simply be closing and opening the channel.

They don't seem to have variable attenuation based on the acoustic energy, though. If the soldiers find them to be acceptable everyday gear at all, there would certainly be funding available to engineer improved internals.

The over-ear comms-integrated rig is priced at double my estimate for what an in-ear version might sell for, which tells me that I was probably underestimating.

Most of the hearing protection I've used when shooting seemed designed to disrupt the sound wave move than actually reduce it.

You can achieve reasonable short-term protection by holding your hands flat over your ears. It doesn't reduce the subjective volume, but it does [anecdotally] prevent subsequent symptoms that indicate temporary or long-term damage has occurred.

> You can achieve reasonable short-term protection by holding your hands flat over your ears.

Not flat... that won't do much. They must be cupped... basically you make a letter "C" with your hands then old that up to your ear with your side of your palm (pinky side) resting on your temple.

This will deflect the sound wave around your ear. Old-school artillery trick.

This is how the Brits do it http://i.telegraph.co.uk/multimedia/archive/01394/20030330-R...

Thanks - I was thinking in comparison to "sticking fingers into ears", could've phrased it better.

With most ear plugs you can hear normal conversation without any problems. Certain sounds are blocked out more and things like music sound distorted.