Possible meanings:
* Imitating a sound: He might be mimicking the sound of someone slurping a drink, a noodle, or something else. This could be done playfully or mockingly.
* Expressing enjoyment: The sound could be a way of expressing enjoyment or satisfaction, perhaps after eating something delicious.
* Being silly: He could be making the sound as a silly joke, with no particular meaning behind it.
* Teasing: He could be teasing someone by imitating a slurping sound, particularly if they are known to eat noisily.
* Disgust: In some cases, the "slurp slurp" sound could be used to express disgust or disapproval, as if someone is being unpleasant or making a messy sound while eating.
To understand the meaning, consider these factors:
* The boy's age and personality: Younger children might use the sound more innocently, while older boys might use it more playfully or sarcastically.
* The context of the situation: What was happening before the boy said "slurp slurp"? What was the tone of his voice?
* The body language of the boy: Are they smiling, frowning, or making other gestures?
To get a better idea of what he means, try asking him directly: "What are you doing?" or "What does that sound mean?" This will help you understand his intentions and avoid any misunderstandings.