Simple sound experiment - I filled plastic cup with water and placed directly on speaker cone. Then used SineGen to generate sine waves from 300Hz down to 15Hz. Result is similar to cornstarch videos in YouTube, only everything is happening much faster. Maybe I'll try something more viscous next time (see upd.#1). Interesting note: sometimes vibrations are in sync with light bulb 50hz frequency, sometimes with cameras 30fps and sometimes it simply resonate. All this variety gives interesting wave dance.
Upd.#1 - tried natural oil, nothing interesting. (less info)