What is the ruling on listening to sounds that increase concentration, intelligence, and memory, such as sounds that increase alpha and gamma brain waves, if they do not include music?

We do not know the nature of the voices being discussed. However, the default ruling for things is permissibility. There is no harm in listening to all natural sounds, with the exception of musical instruments. As for what was mentioned about the effect of these sounds on concentration and memory, we have no knowledge of it, and it cannot be proven or disproven without established scientific studies.