If you want 16-bit sounds, sfxr and bfxr are good programs to create them. I usually use sfxr, but bfxr has more options. You can convert (and/or edit) the wav files into ogg format with other programs, like Audacity. To compose 16-bit chiptunes, Famitracker is a good option, but it takes some time to learn it and you may need to look for decent tutorials or examples made by others. Famitracker can be used too for more complex sounds that you cannot do with sfxr/bfxr, and later you can edit them with Audacity.