I hear a lot among Bambara speakers this word that similarly sounds like ɲɛ and can be used in similar situations.
For example hearing: “O ka nɔ” or “o ka ɲɔ” after describing something you have done.
I believe this word used for emphasis but do you all think?
Can you provide more context abut the potential examples?
It would be helpful because the ka could either be the predicate marker for a qualitative verb ("O ka ɲi ‘That is good’) or it could be the optative predicate marker that shows up in sentences like An ka taa, but in a passive voice like: O ka dun! ‘That shall be eaten’!
And are you sure that we aren’t talking about ɲi meaning ‘good’?
No, I feel like this word is different from ɲi because for example when I ask about the family like: “Somɔgɔ ka kɛnɛ?” a Bambara speaker may respond like “U bɛɛ bɛ nɔ”, which I believe means ‘they are all good’.
Ah! This is very different!
They are saying: U bɛɛ bɛ yan nɔ (‘They all are here’), but the yan (‘here’) is truncated to a very subtle y that sounds like a single vowel sound like [i]:
U bɛɛ bɛ y(an) nɔ
'They are here
This use of nɔ is an archaic postposition that generally means ‘in’. It also takes the form rɔ in expressions like su rɔ ‘last night’, but in the above example it turns into nɔ because of the nasalization at the end of yan.
In Maninka, the word is normal and generally takes the form rɔ or dɔ:
À ye ji dɔ
‘It is in the water’
Note that you could also simply say the original sentence without the postposition nɔ:
U bɛɛ bɛ yan
‘They all are here’
Having learned Jula first, I only came across the use of this “extra” nɔ once I lived in Bamako. It strikes me as a very Bamako or standard “Bambara” way of speaking.
Perhaps the other word I referred to that sounds like ‘ɲo’ that I hear only in sentences similar to “O ka ɲi” originated from french’s “non” to give emphasis that something is good. Here is an example from an audio.
Ah! Now I see what your original question was about! (But you were missing the word ɲi in your original example 
)
I have transcribed part of the recording (in case the above link goes dead later).
The context is a female friend sending a voice message in response to a suggestion or request that you all speak in Bambara (or something like that); I have flagged the word that you originally wrote as “nɔ” as o here because that is my best guess as the candidate word that I already know of:
O ɲɛna. I b’à fɛ ka kuma bamanankan de la? O ka ɲi o. O ka ɲi o. Bamanankan ka ɲi o.
It’s clear that you friend is saying O ka ɲi, etc. And yes, then there is something that trails the word before the end of her utterance. As you suggest it seems to be a word for some kind of emphasis, but which?
I think that it is possible that it’s a use of a French loanword non (‘no’, used to mean something like, “right?” in English), but the more likely candidate is o (sometimes written wo) as a particle (in other languages they are called “modal particles”).
O (or ó with a high tone) is a modal particle that is in the dictionary and generally appears at the end of a sentence:
In Bamadaba, it is listed as a particle that expresses “empathy”.
In the use case that you’ve flagged (which is something that I have also heard many times from Bambara speakers, but never thought to investigate 
), I think that we are potentially hearing o, but that it is influenced in speaking the preceding sounds ɲi (which is considered nasalized [e.g., ɲin] in other spelling systems like N’ko) and therefore sound like no.
In any case, that’s my best guess for now! I could reach out to other linguists, researchers or experts at some point and ask…or maybe one of them will join this forum!
Let me know if that helps!
Otherwise, what is sure is that my explanation about the postposition nɔ above stands and that it is a completely different word and usage than this instance of O ka ɲi o.
Following up on this, I asked some fellow linguist specialized in Manding and Mande languages and they agree that it is likely a/the particle o (though one person believes that it is low rather than high tone; which is different than what is found in the dictionary and Bamadaba).
More chiming in from linguists:
Selon moi, il s’agit d’une particule dicto- modale de ton bas, sans nasalisation aucune. Il ne s’agit pas de la particule d’empathie du Bamadaba à ton haut, ni de la particule d’apostrophe ò , de ton bas: muso ò « eh, toi la femme » ni de la conjonction distributive notée ô dans la Bamadaba, mais dont le ton peut être haut : í yé ó yé « chaque fois qu’on te voit “
– Boubacar Diarra
And:
Pour moi, (c’est) ó [wó]
traduction: ‘pour de vri’, ‘certes’– Kalilou Téra
