It would probably sound like a synth kick drum.
A common technique for making a kick is to take a low-frequency sine wave and apply a short envelope (with zero or near-zero attack) to both frequency and volume. So you start out with a high pitch that rapidly goes back down again. Most envelope generators have an exponential decay shape rather than a 1/x shape, but they're pretty similar (1/x in red, exp decay in blue):
!