Something major changes within our speech and/or auditory systems after early childhood. We lose the ability to learn fine differences such as the accent. It's

Something major changes within our speech and/or auditory systems after early childhood. We lose the ability to learn fine differences such as the accent. It's not clear whether this is a difference in the way speech (sound) is perceived, or our ability to pronounce, or something in between. Sure, accent is not pitch, it's more like timbre. In any case, both are related to the ability to do spectral analysis of the sound, and act upon it.