Muffs and plugs
I have commented on this subject before, but every one prefers anecdotal evidence instead of clinical data!!!
First, Any well made foam plug INSERTED PROPERLY will give you about the best sound attenuation possible.
Let me explain again;
If your ear canal is completely plugged, you will have 40-45 dB of sound reduction. That is about 100 to 200 to 1 reduction. The reduction is limited by your mastoid bone as is passes sound from your skull right to your inner ear with about 40-45 dB reduction. That is the maximum you can get, makes no difference whether you add muffs or not.
The reason ear plugs are rated at NRR or noise reduction rating, is that OSHA wanted a useful rating system that accounted for mis-insertion of plugs. What the manufacturer must do is first, measure the best attenuation their plugs can do, and it often is 35-40 dB attenuation. Then they have to figure out the reduction in attenuation by mis-insertion and subtract that from the best number. Hence, a foamie rated at 33 dB when it can do maybe 40dB. People have been seen with yellow foamies sitting sideways horizontally in the bowl of the outer ear!
the reason some new high quality muffs seem louder than an old pair is that they may have a compressor amplifier that amplifies softer sounds normally, somewhat louder sounds get some attenuation and really loud sounds are limited by the amplifier to a maximum of around 115 dB SPL and the old mastoid bone reduces the 160 dB gun blast to 120 dB so that is why it still sounds loud. But, 120 dB impulse noise is not necessarily bad as the energy in a blast attenuated by 40 dB through the mastoid bone is less that a steady 120 dB sound, which is on the threshold of pain.
Personally, I will not use muffs as they never seal as good as one would like, hence the relatively low NRR rating. Sure, you can put in yellow foamies too, but you can't hear your neighbor talking anymore. With active muffs, you can hear softer sounds just fine.
I use Blast protectors from Etymotic Research. They have a high quality hearing aid compressor amplifier that amplifies soft sounds, mildly attenuates medium noise and limits loud sounds.
Sure, they are expensive, but they protect my hearing, what's left of it, and they allow me to hear lower level sounds. Let's see, you will pay $2000 for that new NF Comp scope, but $400 is too much for a safe pleasurable hearing experience?
And, yes, I'm an electrical Engineer and I did do the masters program in audiology. And I did work in the hearing aid industry. I don't do anecdotal evidence!
Norm Matzen