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EngineeringELI5: how do high fidelity ear plugs work?
(self.explainlikeimfive)submitted 3 years ago by halfpastwhoknows
I’ve been using different kinds of ear plugs at festivals and concerts for 5+ years now. I love my cheap high fidelity plugs because they decrease the decibels without muffling like foams ear plugs. As far as I understand this is magic. Please ELI5.
[–]Delehal 2 points3 points4 points 3 years ago (2 children)
Foam earplugs muffle high-frequency sounds a lot more than they do low-frequency ones. It's similar to the effect of a sound board running a "low pass" filter.
High fidelity earplugs are designed to muffle all frequencies of sound more evenly, so the sound you're hearing has a lower volume but it's otherwise much closer to the original sound.
As for how they do this, you may notice that they are usually hollow. They're designed to more closely mimic the regular acoustic environment of your ear canal.
[–]halfpastwhoknows [S] 0 points1 point2 points 3 years ago (1 child)
So it’s still ‘muffling’ just doing a better job than foam.
Yea, I know they are hollow but I don’t quite understand the physics of it. Is it a specific shape or just making it harder for noise to get through? Where does the dampening happen?
[–]anonymous13781378 1 point2 points3 points 3 years ago (0 children)
the dampening (or 'muffling') happens because of something called a 'sound bore' that is located inside of high fidelity earplugs, which is one of the qualities that differentiates itself from foam earplugs (and that high fidelity plugs can be made custom fit--this also helps with sound quality because it mimics the anatomy of your own ear).
the sound bore is this tube that runs through the high fidelity earplug. in this tube, air (with sound in it, because sound travels through air into our ears) gets caught here. this air acts as a mass that plays against the acoustic signal, thus muffling both low pitch AND high pitch sounds. this gives the sound a more natural quality at a lower loudness level.
[–]Elitetoday -1 points0 points1 point 3 years ago* (2 children)
What does it do?
It tries to equally tone down all frequencies of hearable sound spectrum to enjoy music at the lower sound level without changing it.
How does a normal ear plug work?
Music is a combination of sound waves, from those waves the frequency is the tone and the amplitude is the intensity. You get different sounds by changing he intensity of different frequencies.
Looks kinda hard, but you only have to remember that we need to lower the amplitude to tone down the music, but we have to do this for every frequency relatively equally.
For example, if we have a two-tone music piece, 1Hz with 20 amplitude and 20Hz with 10 amplitude. If we change this to 1Hz with 15 amplitude and 20Hz with 5 amplitude, the music changes. But 1Hz with 10 amplitude and 20Hz with 5 amplitude is the same as where we started with but less intense. Reducing the amplitude of frequencies we call attenuation.
Solid material is typically very good at attenuating high frequencies but bad a low frequencies, that is why you can easily hear the bass of of the sound from your neighbors. That is also why normal ear plugs sound muffed, because the solid material is attenuating similarly.
How does a high fidelity plug work?
We need to find a way to attenuate without discriminating between high and low frequencies. Also, your ear isn't a perfect microphone either, specific frequencies are better perceived than others. To have a same sensation of music we need to keep that in mind as well.
These specific plugs usually have 3 to 5 'dishes' on them. These dishes work as a kind of bandwidth attenuation, specific ranges of frequencies are attenuated well, others not. By this way we can design a plug that attenuates music any way we want.
So we can make plugs that block low or high frequencies, or block only around a specific frequency, by carefully placing and designing these dishes.
The high fidelity plugs are designed to closely match your ear but lowering by a specific factor. Exactly what we want.
[–]halfpastwhoknows [S] 0 points1 point2 points 3 years ago (1 child)
How critical are those rubber rings? My current pair has only two and I’ve seen some like Earasers with just the one cup.
[–]anonymous13781378 1 point2 points3 points 3 years ago* (0 children)
the rubber rings are not really that critical. although they do help to better match the anatomy of the ear canal than a standard foam plug (the rubber rings, although not as good as a custom mold, do help a bit with the quality of the sound as well as retention in the ear canal), the acoustic quality/dampening all tie back into the sound bore that i explained in the above answer :)
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