إِنَّهُ يَرَاكُمْ هُوَ وَقَبِيلُهُ مِنْ حَيْثُ لاَ تَرَوْنَهُمْ إِنَّا جَعَلْنَا الشَّيَاطِينَ أَوْلِيَاء لِلَّذِينَ لاَ يُؤْمِنُونَ
He (shaitan) surely sees you, he as well as his host, from whence you cannot see them; surely We have made the Shaitans to be the guardians of those who do not believe. (Sura al-A’raaf, 7:27)
One thing to note of is that we do not hear the Waswasa of the Shaytan and each of us has been assigned a Qareen which will company him to encourage or motivate him to perform some sort of sin, Mainly this Waswasa will be on the form of thoughts but the nature of humans and the intelligence we possess will always cause us to think constantly towards different aspects.
As we have desires this might be something the shaytan will take advantage of, these desires may be something we are thinking about therefore a shaytan will try and encourage you to follow these desires knowing these desire resulting in gaining more sins, these are all thoughts flying about in your brain therefore you will not be able to separate your thoughts to your own mind and waswasa, if you refer to the below hadith you will relies that the companions are referring to the waswasa as thoughts.
The Sahabah/companions of the Prophet (may Allah be pleased with them) also faced this problem. It was narrated that Abu Hurayrah (may Allah be pleased with him) said: “Some of the companions of the Messenger of Allah (peace and blessings of Allah be upon him) came to the Prophet (peace and blessings of Allah be upon him) and said to him, ‘We find in ourselves thoughts that are too terrible to speak of.’ He said, ‘Are you really suffering from that?’ They said, ‘Yes.’ He said, ‘That is a clear sign of faith.’” (Muslim).
It was narrated from Ibn ‘Abbas (may Allah be pleased with them both) that a man came to the Prophet (peace and blessings of Allah be upon him) and said, “I think thoughts to myself, which I would rather be burnt to a cinder than speak of them.” The Prophet (peace and blessings of Allah be upon him) said, “Praise be to Allah, Who has reduced all his [the Shaytan’s] plots to mere whispers.” (Abu Dawood).
I don't think you will be able to classify a waswasa from carnal could, as shayateen like i said will always try to find ways to make you disobey Allah one of these ways can be through your carnal soul, lets say for example every man has a desire for women this is only natural a shaytan may use this desire to encourage you to look at things you shouldn't be looking at.
Main thing is we should control our desires and seek refuge to Allah whenever wrongly thoughts occur in our minds and not obey them, as Muslims who follow the Quran it is clear for us to tell right from wrong, therefore we know which thoughts are right and which are wrong and sometimes we may have a chain of wrongly thoughts which disappear when we seek refuge to Allah.
وَقُل رَّبِّ أَعُوذُ بِكَ مِنْ هَمَزَاتِ الشَّيَاطِينِ وَأَعُوذُ بِكَ رَبِّ أَن يَحْضُرُونِ
And say: O my Lord! I seek refuge in Thee from the evil suggestions of the Shaitans; and I seek refuge in Thee! O my Lord from their presence. (Sura al-Muminun, 23:97-8)
Similarly elsewhere in the Qur’an, Allah (S.w.T.) says:
مِن شَرِّ الْوَسْوَاسِ الْخَنَّاسِ
Say I seek refuge from the evil of the whisperings of the slinking (Shaitan). (Sura an-Naas, 114:4)