th vs f vs s

I’m cognizant of the difference among the unvoiced “th”, “f” and “s”, and I know that they sound somewhat similar to the average non-native speaker, like myself.

I’m wondering how native speakers perceive them. Do they sound somewhat similar to them?

My auditory perception of them is
The “th” and the “f” sound a lot more similar than the “th” and the “s”.

So, please weigh in on this. I’m really interested to know your take on this.

Well, I am a native speaker - first I had to figure out what an “unvoiced th” sound is :). I think I got it - think is unvoiced, right? To me, it does not sound much like either an f or an s. If the unvoiced th is at the end of a word, it does sound a bit like “f”. Many children learning how to talk would pronounce both like “bof” or tooth like “toof”. But it is still a pretty obvious error as the sounds do not sound very similar to me.

Thanks a lot!
Yes, the unvoiced “th” is in think. :))
I asked because to me the difference between “th” and “f” sounds very tenuous, barely noticeable, and I’m liable to mix them up and sometimes it’s tough for me to tell apart words like “think” and “fink”. And not only for me, but for many non-native speakers. Hehe. But from your reply I gather it doesn’t apply to you, although you do find them similar.
Alctually mixing up “th” and “f” can result in quite embarrassing situations: I’ve heard of folk tales where students unwittingly said “feces” in leu if “theses”.

I reckon it’s something you get the hang of as a kid, and adult learners struggle with it.

A percentage of native English speakers, particularly children, have this th/f problem too (and not just at the end of a word as Luschen says). Most learn to differentiate but with a small number this continues into adult life (sadly, their own children often then have difficulty differentiating the sounds because their primary speaking example is getting it consistently wrong.

th sounds as s and f because you don’t have the image of its sound in your mind. All unknown a human mind interprets basing on already-known in his mind. Keep working on listening and articulation, and you will tell apart these sounds.