Weird whirring sound coming from my engine at certain speeds?

I own the vehicle listed above Lapin - slightly different from the Alto, but that model was not an option on the site since they are only offered in the Japanese market.

I’ve noticed a weird sound coming from the engine at 40kmh and 50kmh, and only when those speeds are maintained. If I’m accelerating above that, I don’t hear the noise. The noise is kind of like a high-pitch hum, with a sort of whirring aspect to it.

I’ve heard that it might be the radiator fan making that noise but wanted to get a second opinion before I bring it to a mechanic.