According to an embodiment, the audio holes 145a, 145b, 147a, and 147b may include speaker holes 145a and 145b or microphone holes 147a and 147b. One of the speaker holes 145a and 145b may be provided as a receiver hole for voice calls, and the other may be provided as an external speaker hole. The microphone holes 147a and 147b may have a microphone inside to obtain external sounds. According to an embodiment, there may be a plurality of microphones to be able to detect the direction of a sound. According to an embodiment, the speaker holes 145a and 145b and the microphone holes 147a and 147b may be implemented as one hole, or a speaker may be included without the speaker holes 145a and 145b (e.g., a piezo speaker). According to, the speaker hole indicated by the reference number “145b” may be disposed in the first structure 101 and used as a receiver hole for voice calls, and the speaker hole indicated by the reference number “145a” (e.g., an external speaker hole) or the microphone holes 147a and 147b may be disposed in the second structure 102 (e.g., one of the side walls 123a, 123b, and 123c).