Hey, sorry for the delay and long reply, I wanted to cover everything you asked.
Yep, I have considered TTTS or stapedius spasm in the early days but started to move away from it as it doesn't appear to explain a lot of the unique traits/isn't solved with cutting in nearly all cases I saw. In a way I'm sure many of us hope it would be that since we have physical access to cut it/it may change over time.
I think the suppression from loud noise is far more likely a temporary threshold shift (than long term muscle spasm unless you have any evidence?), which happens any time you are exposed to loud sounds, it happens at all effected frequencies and in the cochlea.
Here are some more reasons why I don't think it's tensor tympani/middle ear reflex related.
- Tensor tympani is generally known to create loud pops/clicking and low muscle rumble/roar (put a tensed fist to ear if you want to get an idea) - both of these can be stopped by cutting the muscle. However, there is close to zero success stories with cutting the muscles to stop the sub hum.
- The frequency pitch of the hum is seemingly stable, which spontaneous otoacoustic emissions and regular tinnitus generally are. If it were muscle tensing you'd probably experience a variety of speeds/frequencies/clear fluttering.
- The fact that some people experience amplification of quiet bass sounds suggest it is amplification related, which is mostly the responsibility of outer hair cells.
- Only bass frequencies or sounds with some bass suppress the hum. Sounds with bass EQ'd out do not. Possibly suggesting it to be isolated to a specific part of the cochlea(apex) either inner or outer hair cells.
- Tensor tympani reflex: Loud sounds in one ear are known to create an acoustic reflex in BOTH ears - however, with the hum, playing bass in opposing ear(headphones) does not stop the hum in the other.
- However, low buz/hum has been reported with the less popular "stapedius spasm". So maybe something to look into there?
I rarely get temporary threshold shifts in upper frequencies when I wear earplugs (last 13 years) as they are easily blocked out. However, low frequencies remain far less protected by earplugs. So it's quite possible we're still able to experience some kind of threshold shift/inhibition there when going to loud places or a plane ride with 85-90 dB of sub for hours, maybe even some form of damage over time for louder volumes. Temporary threshold shifts last few a few days, correlating with our suppression experience for several days.
Is there evidence that suggests the tenor tympani also remains tensed after noise exposure?
From what I understand those two muscles are engaged based on volume signals via hair cells, the brain then sends messages back to the muscles with different 'efferent' nerves to create the reflex. so maybe there is a connection there, i.e. muscle flutters because its getting confused signals in the damage low freq cells, but likely not due to the stability mentioned above.
To answer your other questions...
I haven't found that loud sounds make it directly worse, especially not in the days after exposure which is why it's tricky. If anything is gets better/disappears temporarily. I know someone who said once he stooped caring and continued living his life it went away. Meaning he stopped avoiding sound and just continued on going out etc. which long term seemed to suppress the symptom.
Yes, I wear earplugs even in restaurants as I experience a distortion in one ear with sounds above 77 dB or so. And now I'm paranoid about bass so I even wear them on planes (eek). Otherwise no, I wouldn't need them at that level.
I definitely wear them at a bar or club. Gotta remember that even if the volume is only 85 dB in a bar, someone is shouting in your ear at 100 dB AND dB(A) ratings don't even measure bass, it's excluded. So when you have a 95 dBA reading in a bar/club you're probably being exposed to 105 dB of subs. Same goes with cars and plans which are significantly bass heavy. Even though low frequencies are vibrational and harder to damage, you'd think the fact we can't protect them properly may play a role in all this? Then you'd also expect flight attendants to have this issue after 15 years which i haven't seen.
One part of me wants to believe that this isn't related to damage at all, and feeding the ear low sound actually suppresses this weird symptom for whatever reason, which would be great it if it was simply the tensor tympani muscle. However, that feels like wishful thinking, we'll know with more time I guess.
Based on everything I've read I believe SOAE better explain nearly all the unique traits of low hum tinnitus. I promise to outline the full theory when I have more time to finish reading up. The good thing is SOAE aren't usually associated with damage and also they are objectively audible by special microphone. So I might look into getting that tested. It is even mentioned as a cause for the TAO HUM people hear: reddit.com/r/TheHum/comments/qtd09w/what_is_the_hum_explained/
When I saw a guy who has researched the topic for years saying this, it really made me more confident.
Also, here's an example of how earplugs don't protect the low frequencies, which is scary to me and could be an explanation as to possible damage in the low frequencies at least for my personal case. Whether this damage be traditional hearing loss or mechanical. Low frequencies vibrate a lot and could potentially be moving something else. Could also just be a coincidence as it has long been thought near impossible to damage low frequencies significantly.
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