In detail, the pronunciation starts with the sound /bə/, which is represented by the letter 'b' followed by the schwa sound ('ə'). This sound is a weak vowel, similar to the sound in the word "about".
The second part of the pronunciation is /ˈluːn/, which is represented by 'loo' followed by the letter 'n'. The 'loo' sound is a long 'oo' sound, like the one in the word "moon". Finally, the last sound is the letter 'n', pronounced as the consonant sound /n/.
So, when saying "balloon," you would pronounce it as "bə-LOON."