Here's another perspective re the squealing bud episode, or...

Here's another perspective re the squealing bud episode, or maybe it's just an interesting story lol:

I've been tinkering around with my Max buds (gen 3).

The buds have an infrared (IR) sensor located beside the ear tip and facing the skin. This sensor wakes up some of the internal circuits but the buds don't become fully operational with this alone.

One bud in a pair behaves as the master and connects to a phone (or whatever) via Bluetooth. The other bud behaves as a slave but it needs to communicate back and forth with the master for a variety of reasons. The system seems to achieve this using a separate low power radio (RF) signal which would have to be independent of the Bluetooth. The buds only fully wake up when the slave receives the RF signal plus both IR systems are triggered. I've tested the range of the signal by removing one bud from my ear and moving it away from my head and noting when the system shuts down (see below for how I kept the IR sensor working). It's about 20 cm or so. One point to keep in mind is we don't know exactly what is still powered up in the buds when they lose RF contact with each other. But I think we can say that the RF system is powered up in any bud when it's IR sensor has been triggered.

But hang on, shouldn't the bud that I removed from my ear have powered down due to the IR sensor. To get around that, I put that bud in my hand with the tip lodged between two fingers which puts the IR sensor against some warm skin. I could then sway that hand around to see what happens to the RF system. An important point is that Justin was holding the gen 3 bud in his hand exactly the same way! Assuming it's battery had some charge, some circuits including the radio transceiver would have been active.

But there's a lot we don't know.

Was the gen 3 bud the master or slave (left or right ear) and was it's battery holding a charge.
Were the gen 4 buds sitting correctly in their case.
- Justin seemed to be still fiddling with one of them when this happened which means it could have been active, at least partially.
The gen 3 buds certainly aren't capable of making that much noise. Would the gen 4 be any different?
- My test indicated that the squeal from a gen 3 bud not in the ear but nearby was barely audible.
- In any case, I would expect that the audio amplitude applied to the diaphragms would (should) be very limited by design.
- So where did the loud noise come from?
I assume there would be similarities in the gen 3 and gen 4 system designs even with different chips.
- Could there have been some interaction (via the RF signal) between the two. Do they use the same frequencies?

To sum up (IMO):
There's too many unknowns from our perspective to pinpoint exactly how the problem occurred.
But even if there is a minor design issue the circumstances were very unusual - would a gen 4 user happen to have a gen 3 in their hand and oriented in such a way as to trigger the IR?
The engineers will certainly be trying to replicate the problem to see exactly how it happened and what needs to be done, if anything.
The most serious aspect is whether the hardware in a bud, gen 3 or gen 4, is capable of generating that much noise. We assume the answer is no, but if it is capable then that would be a serious safety concern and might involve minor hardware changes to limit the power.