1. Silence: This is the most straightforward answer. Silence is the absence of sound, the opposite of something audible.
2. Visual: This refers to something you see rather than hear. So, the opposite of a sound could be a picture, image, or video.
3. Touch, Taste, Smell: These are other senses that are the opposite of hearing. You could say a touch, taste, or smell is the opposite of a sound because it is experienced through a different sense.
4. Absence of Vibration: On a more technical level, sound is caused by vibrations. The opposite of a sound could be the absence of vibration.
Ultimately, the "opposite" of sound depends on how you define it and what you want to express.