"Y" is the symbol of Lenovo Idealpad's Y** series, which is mainly equipped with Y430\Y530\Y550\Y450, etc. It is equivalent to the trademark of Y series products and has no practical use.

Also, that’s not an upside-down U. It’s a symbol for headphones. Look carefully. I guess the reason for having this headset is to match the entertainment features of the Idealpad series of products.