Kikoeru? (聞こえる?) is a Japanese word meaning "Can you hear (me)?" or "Is that audible?". It's the informal, question form of the verb kikoeru (聞こえる), which means "to be heard," "to be audible," or "to understand (when hearing)."
The word is commonly used in situations where the speaker wants to confirm if someone else can hear them, especially when there might be a problem with the connection, sound quality, or ambient noise. It can also be used to ask if a particular sound is audible to the listener. The question mark is crucial as it denotes the interrogative nature of the utterance. Without it, Kikoeru would be a statement, meaning "It can be heard."
The word implies a degree of casualness, so it's generally used among friends, family, or people in informal settings. In more formal settings, a more polite form, such as Kikoe masu ka? (聞こえますか？), would be more appropriate.