Rhune

So, I've got a mk4 ('22) Skoda Octavia with an e-tec engine- As i've been driving it, I've started to notice an extremely short, very high-pitched, very faint tone sounding randomly. Imagine a mosquito quickly going past your ear 😂. It almost sounds like it's behind me in the rear passenger compartement, but really hard to tell with the pitch and faintness of the sound. I've worked out that it always happens when the little "eco" in a circle symbol on the instrument display turns out. Manual says this symbol comes on when the transmission get put into neutral whilst driving. Anyone had this or have any idea what's causing it? Now I've heard the sound I can't un-hear it, and I can't keep driving with the radio at full volume forever!