@cookiejar: While the 3M Peltor X-Series Over-the-Head Earmuffs sells for $25.01 on www.amazon.com in the U.S., in Canada on www.amazon.ca they sell for $53.50 which is over double the price. I'll stick with Bilsom.
The pair I bought several years ago are okay at canceling out airplane rumble, but not much else. Is there any headphone on the market that can cancel all external noise from 0 to 20kHz to a reasonable degree, or are the upper frequencies too difficult to cancel?
Forgot two aspects and just thought of a few more.
As with most NR headphones, you want to be able to play you own music. I have seen products that suppress that signal when an outside signal is detected. Fender in their Passport PAs calls in Priority Interrupt. Sound on input 1 (usually from a mike) suppresses all of the other channels.
A variation on this in the car would be having the car's voice be able to cut in as well. This would be selectable if the passenger did not need or want it. Which leads to the next variation: headpones such that the driver can listen to whatever while the passengers sleep.
I think I am getting close to a product that might be called Google Aureality. (Always good to come up with the product name if you can.)
Eventually of course, this and those geeky Google Glass things will be miniaturized into chips to be implanted in the heads of the ultra-chic. Actually, a few more shrinks and cell phones will actually be the size of cells. tres efficient.
I was thinking of the phrase, Great Googlemy-Mooglely. This may be Max the Magnificent dressed up for Halloween (or ESC-Mardi Gras) with all possible wearable electronics.
I think that somewhere between the in-ear monitor and the 'normal' NR headphones, we may have a new product idea. You want normal earmuffs to suppress as much 'noise' as possible. You want NR headphones to reduce as much periodic noise as possible. The NR headphones can do better on low frequency periodic noise than ear muffs can. Now, the trick: The NR headphones cannot filter out music from the environment without filtering out speech. What if we supply the music signal via another means, say a bluetooth connection from the car radio. Now the DSP in the NR headphones can run an algorithm to get the 'average' delay of the sound from the speakers vs that from the Bluetooth signal. Key: The Bluetooth signal will arrive several milliseconds before the sound from the car speakers. The DSP software should be able to then control the speakers in the NR headphones to cancel some or all of what comes from the speakers. That is, you can adjust the volume down (if you just find it too loud) or cancel it. This could work for some of the frequency bands at rock concerts. This gets complicated with multiple speakers, but I bet it would work for two as long as you were not moving head too much. Most importantly, the regular NR function would allow other non-periodic sounds to get through. Eg, requests from she who must be obeyed to open a can of caffeine so she can keep driving. Or asking you too explain what you and her beautiful cousin were doing in that pirogue down on the bayou.