Apple Airpod Pros as active & "intelligent" earplugs

[Reezekeys]

Nice to hear these helped you. I'm very much hoping Apple is exposing the transparency controls to developers, and someone comes up with an app geared for musicians like us. I would want more control over the amplification - right now it seems like the range is between "some" and "a lot." It would be good to let us start at zero and add in only what we need to hear clearly – that would make these more useful for louder gigs, I think. Displaying db levels would be good too, that seems like it should be doable.

[MathOfInsects]

Just now, Reezekeys said:

Nice to hear these helped you. I'm very much hoping Apple is exposing the transparency controls to developers, and someone comes up with an app geared for musicians like us. I would want more control over the amplification - right now it seems like the range is between "some" and "a lot." It would be good to let us start at zero and add in only what we need to hear clearly – that would make these more useful for louder gigs, I think. Displaying db levels would be good too, that seems like it should be doable.

I have a student who is a scientist and takes a more than casual interest in wave theory and the physiology of hearing. He has some cool high-tech hearing aids. I mentioned something about this discussion of the use of transparency mode and he said not only is it beneficial for those with hearing loss, but that the Airpods will directly import the specialized settings of the hearing aids, and that he'd written to the tech team to commend them on this amazing and unnecessary bonus and heard back directly from one of the techs who developed them.

 

[Reezekeys]

29 minutes ago, MathOfInsects said:

the Airpods will directly import the specialized settings of the hearing aids,

 

Correct, as I mentioned in the hearing aids thread. You can import an audiogram in a few ways: use an app called Mimi to self-administer a hearing test on the iPhone, which generates an audiogram that the Airpods use to create an EQ curve to compensate for the losses shown on the audiogram. You can also have a audiogram done by an ENT, then take a picture of the graph, or manually enter the figures (the most accurate method).

[MathOfInsects]

Amazing.

(I don't believe I saw the hearing aids thread.)

[aronnelson]

I have the AirPods Pro 1, looking forward to getting version 2 and trying this.

[sam6599643]

On 5/25/2023 at 3:45 PM, Reezekeys said:

I had a gig last night with a “little big band”, an ensemble of six horns & three rhythm, in a very small & live space. On my way there I realized I forgot my foam earplugs, then remembered my new 2nd-gen Apple Airpods Pro’s “adaptive transparency” feature. I decided to put it to the test rather than stuff my ears with toilet paper.

 

The transparency setting on Airpods Pros is where its built-in microphones send outside sounds to the bud’s drivers and gives you a few controls for what the DSP does with that outside sound. “Adaptive transparency” is Apple’s term for their update to the “regular” transparency setting of the original Airpods Pro. In not so many words, it’s a limiter; loud sounds are reduced in volume. That sounded like something that might work for a musician playing with a loud band! I hate wearing foam plugs as they muffle the highs, and I haven’t had good experiences with either custom-molded plugs or “musician’s earplugs” that claim even fr.

 

I’m here to say these beat the hell out of foam earpugs! I could hear everything with clarity (nothing sounded muffled) and the stage SPLs were much reduced - at one point I pulled one of the buds out of my ear to confirm that. Of course that’s mostly due to having these sealing your ears in the first place - same as in-ear monitors do. I didn’t hear anything that sounded “squashed” to me, as a traditional analog limiter might do. One strange thing I noticed is that these “DE”-verbed my sound! On certain slower pieces I like to add verb to my keys and despite cranking it up pretty high, I couldn’t hear any being applied. I think I know the parameter responsible, so will test with that backed off a bit or turned off. One thing I should probably mention is that to adjust these parameters you must use an iPhone or iPad - doesn't have to be yours though; all settings are retained in the buds.

 

This same “transparency” feature is what I use when I want these Airpods to be quasi-hearing aids, as I mentioned in the hearing aids thread. During the breaks, when I was chatting with people over the din of the crowd, I adjusted the settings a bit (turned up the gain and enabled “conversation boost”) and found I could talk to people in a crowd without asking them to repeat themselves.

 

I got these Airpods to enjoy the ANC on airplanes - not knowing I’d get to take advantage of these other features as well. Further tweaking will ensue, but for now I’m pretty optimistic they’ll make my gigs with louder bands much more enjoyable. I know I sound like an Apple shill but it can't be helped - this is my honest experience. I assume that real hearing aids do everything that I just described and a lot more, and do them better as well - but these were $200, not $2000!

 

Its important to note that the Apple Airpods inherent passive noise isolation/blocking capabilities are not that all that strong.

 

The “adaptive transparency” is based on the “noise cancellation” technology - the appearance of reducing external noise. The appearance of…..which is distinct from actually blocking sound.

 

This means that the Airpods are not a replacement for headsets that actually reduce the total SPL that you are exposed to. So its imporant to beware of what this is an is not.

 

This functionality is useful for a hearing impaired person under normal circumstances. But it’s not going to properly protect the hearing of someone who is on stage and exposed to sound levels that can damage hearing. 

 

You can read a more quantitative assessment of it here:

https://www.nytimes.com/wirecutter/blog/can-airpods-pro-protect-your-hearing/

[Reezekeys]

2 hours ago, sam6599643 said:

The “adaptive transparency” is based on the “noise cancellation” technology - the appearance of reducing external noise. The appearance of…..which is distinct from actually blocking sound.

 

Not wanting to argue as I've expressed some caution about these Airpod's effectiveness in protecting hearing myself, only saying I had a positive experience on one gig. However, one of us is confused because afaik the "adaptive transparency" and noise cancellation features of the Airpods pro are separate and distinct – you can only toggle between those two settings and "off" (where "off" is just using the Airpods as regular bluetooth buds). So, "adaptive transparency" is not "based on" the noise cancelling tech.

 

 

 

Actually, the transparency feature adds sound picked up from the buds' microphones to whatever acoustical sound is making it through the eartips' seal (and music you're listening to from your phone, tablet or computer). The "adaptive" part is just Apple putting a limiter in line with whatever the microphones pick up – so outside sounds beyond 85db (that's the figure I remember) are "turned down." This feature is what got me (and others, according to that article) interested in trying them on a gig.

What I had in mind was to use the Airpod's abilities first as purely passive earplugs to temper the onstage SPLs, then use the transparency feature to add some sound – this to make up for the typical muffled high end I hate to experience when using passive earplugs by themselves. It's absolutely true that any real reduction in onstage sound level hitting the eardrums is a function of only the eartips' seal - the noise cancellation feature has nothing to do with this, since it's not enabled. As that NYT article noted, the silicone tips are most likely not as effective as true foam earplugs in sealing your ear against outside sound. I note that they did their tests by simulating a "loud concert experience" with a clip of hip-hop music. I'm an old geezer and avoid as best I can playing loud gigs! I'm also thinking of getting the Comply foam eartips for the Airpods Pro, they might get me a few more dbs of isolation.

 

As an unrelated aside - while I haven't done another gig with these yet, I've used the transparency feature a lot in the last week just being out & about with my family, and I can say it's made me very happy to have bought these things. I have some hearing loss and fairly loud tinnitus and these make having conversations way easier. I actually had no idea I would be doing any of this when I got them - it was strictly for using the ANC on airplanes, since I do quite a bit of flying!

[jazzpiano88]

If it were me designing the product, I would do something like this off the top of my head:

 

Definitions:

   t = time

   f = frequency

   x = airpod input measurement

   y = airpod output to ear

   k = convolution transparency kernel

   * = convolution operator

   c = crash cymbal impulse response

 

Noise cancellation mode:

   y(t) = x(t) - x(t-1).  (with some smoothing obviously dependent on dt)

 

Transparency mode:

   y(t) = x(t) + k * x(t-1)

 or y(t) = k * x(t)

 

Bill listening mode:

   Y(f) = X(f) / C(f)

 

 

 

 

 

[stoken6]

7 hours ago, JazzPiano88 said:

Bill listening mode:

   Y(f) = X(f) / C(f)

Very good - although I think you have to define the / operator? It can't be simple division - even crash cymbals eventually decay to zero...

 

Cheers, Mike.

[jazzpiano88]

3 hours ago, stoken6 said:

Very good - although I think you have to define the / operator? It can't be simple division - even crash cymbals eventually decay to zero...

 

Cheers, Mike.

i went to the frequency domain for this because it’s going to be approximate spectral cancellation as you don’t have an exact cymbal waveform to be subtractable in time.  / is complex division but C(f) decays over time;  I didn’t specify how to convert Y(f) to y(t); there would always be a cymbal spectrum present in the C signal so you can think of this as some sort of inverse matched filter.  I would imagine it has a buffer and inverse transforms at every t.   I have no idea if this would work (probably not), being kind of a joke, but conceptually I think you could do something in this area.  People subtract sounds from audio but that’s recordings, not real time input.  

[Stokely]

Well, all I know about the Bose pair (gotten as a gift,normally not a fan of Bose) work wonders as baby-crying-on-airplane blockers.   Just made a six-hour flight yesterday.  I could see the wailing kid when I walked by to hit the bathroom, but I didn't hear them    

[MathOfInsects]

18 hours ago, Reezekeys said:

It's absolutely true that any real reduction in onstage sound level hitting the eardrums is a function of only the eartips' seal - the noise cancellation feature has nothing to do with this, since it's not enabled. As that NYT article noted, the silicone tips are most likely not as effective as true foam earplugs in sealing your ear against outside sound.... I'm also thinking of getting the Comply foam eartips for the Airpods Pro, they might get me a few more dbs of isolation.

I am not sure I got that from the article, though I could definitely have missed it. I think the "ANC Off" number is the "eartips' seal" amount for the Airpods (-8dB) and others, and the Adaptive Transparency reflects a 2dB additional cut, for -10dB. Decibels are multiplicative, so that's actually a not-small difference. But it's nothing compared to the "plug-only" models

I'd love to see data with the memory-foam tips in place instead of silicone. I wonder if the design of the Airpods, with that little stem sticking out and hard plastic surface, make them pass more vibrations through than completely in-ear options...? Otherwise, what accounts for any sound at all getting through a completely sealed plug? I'm asking because in that case, the easiest add-on might be a little silicone sheath for the Airpods themselves. 

 

[Reezekeys]

6 hours ago, Stokely said:

Well, all I know about the Bose pair (gotten as a gift,normally not a fan of Bose) work wonders as baby-crying-on-airplane blockers.   Just made a six-hour flight yesterday.  I could see the wailing kid when I walked by to hit the bathroom, but I didn't hear them    

 

My first flight with the Airpods Pro 2 is Thursday. From what I've heard the ANC on these is on par with the Bose so it should be interesting. I've used them in my car; road & wind noise almost totally disappear - it's a little unsettling the first few times you experience this.

[Reezekeys]

If anyone managed to make it all the way through the Apple presentation today, you may have seen a reference to a new listening mode coming to Airpods Pro 2nd-gen: something called "Adaptive Audio" - and it seems to be exactly what I was hoping to see: a combination of ANC and transparency. From macrumors.com:

 

Starting with Adaptive Audio, this feature dynamically blends Transparency mode and Active Noise Cancellation together to deliver the best audio experience in the moment. Apple says that it can tailor the noise control while you move through your environment.

This way, loud or distracting noises surrounding you will be automatically reduced, while other noises will still be audible. Apple gave the example of leaf blowers getting reduced but sudden traffic noises coming through on the user's AirPods.

 

I'm not getting my hopes up too much because this sounds like Apple is going to decide for me which sounds to reduce and which to let through. As that NYT article noted though, when looking at the Airpods Pro as hearing protectors, using ANC by itself reduced the concert volume too much, adaptive transparency not enough. I mentioned in a previous post that it would be cool to combine the two - start with ANC to reduce outside sound a lot, then add only what you need via the transparency feature. This may work better than the limiting "adaptive transparency" does. It'll be interesting to see if this new mode works like that – and if not, whether Apple exposes the parameters to devs so someone else can come up with an app to do it.

[Reezekeys]

5 hours ago, MathOfInsects said:

I think the "ANC Off" number is the "eartips' seal" amount for the Airpods (-8dB) and others, and the Adaptive Transparency reflects a 2dB additional cut, for -10dB.

 

Yea I'm guessing the additional 2db of cut was from the limiter the Adaptive Transparency function activates. However there was no mention of the "amplification" setting this mode provides - I think they said in the comments section they left all settings at their default. That would have put this "amplification" setting in the middle. When I did my gig I had it all the way to the left - minimum. I might have gotten a few more dbs of cut then.

[MathOfInsects]

I've done three gigs with these as my earplugs now.

 

It's a mixed bag, but on balance definitely feels superior to traditional earplugs, not least of which because of how dead easy it is to pop these in and forget they are there--something that you can never do with the moldeds or OTC ones. 

 

I bought the foam tips so I could feel comfortable that one way or another I was still getting ear protection.

 

I love the sort of "calm" drawdown of dB and the ability to hear crisply even at lower volumes. In terms of muffling (or lack it), they are leagues ahead of the clean dB cut in traditional ear plugs. So first impression popping them was, "oh yeah baby."

 

With the whole band playing, though, it's a give-and-take. That's a lot of sound for them to process, and it's not always consistent. Sometimes they would sort of "reset" the transparency, which is disconcerting.

 

They pull the attack back on the drums pretty significantly, and I have to adjust fully to this before I decide if the lack of energy that creates is really a downside, or if it's just new. It also takes the edge off the sound of keys, and same thing, I have to cogitate on this.

Two things though. One is that when I pulled one out to hear something better, I did not hear it better--it was crashy and WAY TOO LOUD and I hadn't realized how well the Airpods were doing. And the other is that they seemed to get a little buggy as the battery wore down (relying on "pre-charge" is definitely a downside), so at the end of one of the shows I swapped them for the earplugs I'd been using (the Earasers) and HOLY SHIT WERE THEY LOUD. Again, I hadn't realized how good a job the Airpods were doing, until I had them stop doing it--which is praise in itself, since it means I'm not really noticing them as they do their thing.

I look forward to the update in the new OS, I'd like to try the noise cancellation on a slider with the AT, since I do think these are borderline not sensitive enough, even though they are an improvement over what I'd been using (which was itself a wake-up call). 

[Reezekeys]

I never heard transparency "resetting", so I'm curious about what might cause this. Also I never experienced any "buggyness" with worn-down batteries, then again I'm not exactly sure where the battery charge was.

 

5 hours ago, MathOfInsects said:

They pull the attack back on the drums pretty significantly, and I have to adjust fully to this before I decide if the lack of energy that creates is really a downside, or if it's just new. It also takes the edge off the sound of keys, and same thing, I have to cogitate on this.

 

I take it you're describing the "adaptive" transparency with the limiter doing its thing. I have to listen a little harder the next time but I don't remember being bothered by this. Maybe your gig was louder than mine, so got more action from the limiter than mine did. For me it was a more subtle lowering in the volume of whatever was loudest in the mix.

 

One thing for sure - like you, I pulled one of the Airpods out while the band was playing, and that really brought home how much volume these were attenuating – it's quite a lot, or at least it seems like a lot.

 

While in transparency mode, where did you have the amplification slider? I've been keeping mine at minimum while playing.

[MathOfInsects]

13 minutes ago, Reezekeys said:

I never heard transparency "resetting", so I'm curious about what might cause this. Also I never experienced any "buggyness" with worn-down batteries, then again I'm not exactly sure where the battery charge was.

 

 

I take it you're describing the "adaptive" transparency with the limiter doing its thing. I have to listen a little harder the next time but I don't remember being bothered by this. Maybe your gig was louder than mine, so got more action from the limiter than mine did. For me it was a more subtle lowering in the volume of whatever was loudest in the mix.

 

One thing for sure - like you, I pulled one of the Airpods out while the band was playing, and that really brought home how much volume these were attenuating – it's quite a lot, or at least it seems like a lot.

 

While in transparency mode, where did you have the amplification slider? I've been keeping mine at minimum while playing.

Interesting to hear you say that about the resetting. I assumed it was from the amount of input it had to handle, but for all I know it's a problem with the set I got. I have to figure out how to trouble shoot that. I'll Google-U that one and see if anyone else out there has mentioned it. 

EDIT: Apple Forums say yes, others have this. No solution or workaround posted yet, I'll watch and see what comes of this.

 

Yes, I started at minimum amplification and added in both a little brightness and a little volume at various times during the gigs, not as a permanent state but when I noticed (for example) the guitar player shredding his butt off and me barely noticing there was a solo. I also played with the ambient noise reduction. When I tried to reduce it, everything seemed too noisy, but it's hard to go backward with something like that. I am going to try starting a gig with that down closer to 0 and see if that lets a couple of frequencies back in that I was missing. 

So right now I'm at hopeful/grateful, but waiting for the OS update. I'd love to push the amplifier and brightness up a bit more and let the noise cancellation on a continuum take care of the dB load. 

Thank you for the tip on this, I feel better about this as a direction than the molded option and much better than the OTC ones. 

[Reezekeys]

1 minute ago, MathOfInsects said:

I'd love to push the amplifier and brightness up a bit more and let the noise cancellation on a continuum take care of the dB load. 

 

Other than the "reduce ambient noise" slider, as far as I know there is NO noise-cancelling going on in transparency mode; they are separate modes. The iOS 17 software update is what promises to combine them, but from what I've read the end user will have no control over this, which is disappointing.

 

I did try noise-cancelling mode for a minute on a gig - it cancels out too much of the music! If there were only a slider to let you vary the amount of noise cancelling, that might be the ticket. The "reduce ambient sounds" slider in transparency mode does sound like a form of noise cancelling but to my ears only affects a narrow band of frequencies, mostly mids & highs, and doesn't reduce the overall volume much.

[MathOfInsects]

8 minutes ago, Reezekeys said:

 

Other than the "reduce ambient noise" slider, as far as I know there is NO noise-cancelling going on in transparency mode; they are separate modes. The iOS 17 software update is what promises to combine them, but from what I've read the end user will have no control over this, which is disappointing.

 

I did try noise-cancelling mode for a minute on a gig - it cancels out too much of the music! If there were only a slider to let you vary the amount of noise cancelling, that might be the ticket. The "reduce ambient sounds" slider in transparency mode does sound like a form of noise cancelling but to my ears only affects a narrow band of frequencies, mostly mids & highs, and doesn't reduce the overall volume much.

Right, completely. I meant with the new OS, your proposed "fix" of a combination of NC and AT is going to be introduced, and I will prefer that, so I can EQ stuff brighter but then lower the overall volume via noise cancellation. I agree, NC is useless on a gig right now, everyone might as well be playing at a different venue down the street. 

I'll be bummed if there end up being no user controls around this, but even off the rack will be an improvement, I think.

[aronnelson]

I was wondering about using the Audiogram as attenuation. I wonder if it could be done?

[aronnelson]

Quote

Two things though. One is that when I pulled one out to hear something better, I did not hear it better--it was crashy and WAY TOO LOUD and I hadn't realized how well the Airpods were doing. And the other is that they seemed to get a little buggy as the battery wore down (relying on "pre-charge" is definitely a downside), so at the end of one of the shows I swapped them for the earplugs I'd been using (the Earasers) and HOLY SHIT WERE THEY LOUD. Again, I hadn't realized how good a job the Airpods were doing, until I had them stop doing it--which is praise in itself, since it means I'm not really noticing them as they do their thing.

 

Just this part is so promising! I think I was using Etymotics with a 15dB filter. I thought it was 18dB but now I think it was 15dB and it still killed the music. The "triangle" newer cheaper ones were a little better at not destroying my guitar sound. I can't wait to try this.

[Ibarch]

My educated layman's understanding of how everything works is as follows. 

 

Noise cancelling works by taking the input from the microphones then doing some calculations to produce a waveform exactly the same but 180 degrees out of phase. By adding this to the headphone output, it cancels out sound from outside that has made it past the seal provided by the earplug. 

For top quality molded earplugs, noise cancellation is not required as the seal should be so good virtually no external noise gets through. 

 

Ambient sound (transparency) is needed because the noise cancelling algorithms have got so good, it cancels most of the outside world. As to how this affects the noise levels reaching the ears, I'm guessing the noise cancelling should reduce it but some articles seem to say otherwise. Have to say I'm not sure on this. 

 

To implement ambient sound,  sound is fed the input from the mics directly into the output. I would expect that is some filtering going on to block out the low end but not a lot else.

 

Regarding mixing, the Sony WF 1000XM range have had settings for years that can adjust the levels of noise cancellation and ambient sound. Other makes may do too. As I'm not in the Apple ecosystem, I've not used Airpods. I am suprised that mixing noise cancelled and ambient sound inputs wasn't included to date, it seems kind of a basic feature. 

 

So, Apple's active transparency is adding some processing to the mic inputs before passing it through. I don't have any knowledge of what that processing is, it may be just simple filtering or some custom DSP algorithms. Apple don't seem keen to share this type of information around.  I don't know if Apple are unique with "active" processing either. I would not be suprised if the likes of Sony, Bose and even the Chinese companies like Anker are not already doing the same or more, just without the Apple marketing to make it sound innovative. 

 

For now, I'm keeping my expectations in check. Apple's statements sound like they are focusing on using active processing for special environments, like a street, busy office or public transport. Effectively only providing a very limited number of "presets". Creating some for stage musicians for varying musical styles probably isn't on their radar this year. 

 

It will be exciting to see where this tech develops in the next few years. It wasnt long ago that splitting up a stereo mix into separate instrument and vocal tracks was science fiction but this is getting seriously good in offline processing. I would love to see it be possible in real time in a set of consumer ear buds! Imagine being able to tap your left bud twice to increase the keys level in your in ears mix. 

 

 

[Joe Muscara]

I came across this article the other day and saved it to share in this thread.

 

https://www.tomsguide.com/features/i-used-airpods-pro-instead-of-ear-plugs-at-a-concert-heres-what-happened

[MathOfInsects]

I played a festival on Saturday, and when the set ended everyone in the group was talking about how prohibitively loud the stage volume was. I'm not kidding when I say I didn't know what they were talking about. The limiter on the Airpods kept it in a completely workable range for me. 

There are still some quirks of sound I have to get used to, or that I might not ever get get used to. But it's definitely a more pleasant way to limit the ambient sound level than traditional earplugs, and more appealing to me than in-ears. It still feels "alive," just not quite all there yet in terms of sound reproduction. But I figure they can only get better from here. 

[stoken6]

Educate me: are the Airpods doing any "active" noise cancellation in this mode? Or is it just the seal of the silicon flange that's actually reducing stage volume?

 

Cheers, Mike.

[MathOfInsects]

15 minutes ago, stoken6 said:

Educate me: are the Airpods doing any "active" noise cancellation in this mode? Or is it just the seal of the silicon flange that's actually reducing stage volume?

 

Cheers, Mike.

Much of the protection is passively provided by the flange, which can be replaced so you have a nice memory-foam seal. The distinction is that, as opposed to other passive protection devices, you can tell the Airpods to send through some ambient sound, and that sound is more comprehensive and natural than what comes through either on passive ear plugs or IEMs. That sound is subject to an internal limiter, and the resulting amount of protection as measured in dBs is greater with the Adaptive Transparency (AT) than the raw passive protection of the plugs.

There is some control of that limiter, so that you can reduce the ceiling a bit, theoretically adding to the protection level.

What there is not (yet) is the other end of the spectrum--Active Noise Cancellation, which would be awesome. Apple is introducing ANC into its AT with the next iOS update; what that will look like is still a question mark.

 

[stoken6]

Thanks @MathOfInsects. This is the bit I don't understand:

28 minutes ago, MathOfInsects said:

That sound is subject to an internal limiter, and the resulting amount of protection as measured in dBs is greater with the Adaptive Transparency (AT) than the raw passive protection of the plugs

So if the Airpods are off/doing nothing, you get a reduction in volume (passive seal), and a reduction in clarity/intelligibility. Adaptive Transparency then adds some sound back into your ears to improve clarity/intellibility - that can only increase the volume compared to Airpods-off, surely?

 

Cheers, Mike.

[MathOfInsects]

6 minutes ago, stoken6 said:

Thanks @MathOfInsects. This is the bit I don't understand:

So if the Airpods are off/doing nothing, you get a reduction in volume (passive seal), and a reduction in clarity/intelligibility. Adaptive Transparency then adds some sound back into your ears to improve clarity/intellibility - that can only increase the volume compared to Airpods-off, surely?

 

Cheers, Mike.

Because of the limiter, it actually adds an extra 2dB of protection over the silicone eartips. (That's not insignificant.) Switching to foam adds more passive protection, and lowering the volume floor of the DSP'd signal that you get from the AT is likely to add to the overall additional dB cut, but it's hard to find proof of this online. The one thing I can say is that the difference between having them in and having them out is massive--much more than the earplugs I had been using--so even if it's only passive protection, it's already better than what I've had. Getting to hear all those frequencies added back in is a huge bonus (for me). I trust what I'm hearing more. 

[Ibarch]

32 minutes ago, MathOfInsects said:

Because of the limiter, it actually adds an extra 2dB of protection over the silicone eartips. (That's not insignificant.) 

 

I'm not sure about this. If my layman's understanding is correct, active transparency is not adding any protection at all. It is quite the opposite. It is feeding sound back into your ears, that had otherwise been blocked by the passive seal. 

 

The limiter may restrict the level of additional noise put back in to your ear but  transparency is always more sound, not any protection against sound.