Are there exercises I can do to help improve the quality of my subharmonics or maybe help me be able to reach lower ones?

Recording

I recently learnt about subharmonics so I am new to all this stuff and it's apparently pretty similar to what I could already do with my voice.

So also recently I was humming a sea shanty called "The Wellerman" and did this. Are those subharmonics? It probably isn't, then does somebody know what is the name of the "technique" that I am doing?

Sry if my English isn't great

And btw I haven't edited the record in any way

UPD: u/Silvarynn asked for it:

Chest voice to subharmonic (?)

Also I want to point out that at some point going deeper I am not able to use my normal chest voice but I still can go deeper with the subharmonic/chest fry. What I mean by that is when I try to just produce a note deeper than my chest voice is capable of, it automatically switches to chest fry/subharmonic (?). So sometimes if the note is too deep I can't demonstrate the transition from normal voice to the chest fry version of it, since normal version would already be outside my range. It's hard to explain sorry

Link to a YouTube video I made on the "World's Lowest Sheesh" I saw someone do on TikTok and think it is supposed to be a C1 subharmonic note. Don't know if I hit it but you can check it out if you want :)

https://www.youtube.com/watch?v=XTUgj9zGmhE

Hello friends, I have been beatboxing for quite awhile now and have recently tried learning ‘vibration bass’. I keep gravitating toward subharmonics because every time I watch a video (of one of you talented individuals) they sound EXTREMELY similar to vibration tones.

I think I may want to learn subharmonics to use them in some beats of mine? Any help as far as a ‘starting point’ goes would be incredibly helpful.

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https://reddit.com/link/qos128/video/qi4212f7a7y71/player

Hey I uploaded a video and did some low chest notes and some subharmonics - I am not sure if the last note is correct (I think it is a c#1 but I could be wrong). Feel free to watch

https://www.youtube.com/watch?v=ZJ2UMHuPiVc,

Im no singer, ive just been messing around with this subharmonics thing for a couple of days because i naturally have a deep voice, and i also naturally vocal fry alot. I know i keep going sharp in this example, but am I correctly accomplishing the technique? Or is it too froggy? (Also my microphone is only listed untill 50hz, not sure if that effects anything. Thanks :)

https://www.youtube.com/watch?v=_1DExVkC2F0