I would think that if elephants are smart enough to learn that recorded buzzing is not a threat then they will also learn that the fake hives don't pose a threat.
Animals can hear way more frequencies than us, in one direction or another - typically the high registers. The recording may sound totally different.
> we used a recording of a disturbed hive of cavity-dwelling Asian honey bees (Apis cerana indica) and conducted sound playbacks to 120 wild elephants in 28 different groups resting under trees in Uda Walawe National Park in Sri Lanka. Elephants responded by moving significantly further away from their resting site in bee playback trials compared to controls. Elephants also increased vocalization rates, as well as investigative and reassurance behaviours in response to bee sounds, but did not display dusting or headshaking behaviour
http://www.cell.com/current-biology/fulltext/S0960-9822(17)3...
Fear of bees is clearly a learned behavior in elephants.