" The vibration of His flute is just like a bird that creates a nest within the ears of the gopis, and always remains prominent there, not allowing any other sound to enter their ears. Indeed the gopis cannot hear anything else , nor are they able to concentrate on anything else, not even to give a suitable reply. Such are the effects of Lord Krsna's flute."
~ Lord Caitanya to Sanatana Goswami

The vibration of Krsna's flute is always prominent in the ears of the gopis. Naturally they cannot hear anything else. Constant remembrance of the holy sound of Krsna's flute keeps them enlightened and enlivened, and they do not allow any other sound to enter their ears.

Since their attention is fixed on Krsna's flute, they cannot divert their minds on any other subject. The vibration of Krsna's flute is represented by the Hare Krsna maha-mantra.

A serious devotee of the Lord who chants and hears this transcendental vibration becomes so accustomed to it that he cannot divert his attention to any subject matter not related to Krsna's blissful characteristics and paraphenalia.

~ Purport to CC Madhya Lila, 21.144