This is the 2039th most frequent Catalan word.
alt
The Catalan word "alt" means "tall" or "high" in English.
Here, 'alt' is used as an adjective meaning 'tall', describing the height of the castle.
El castell és més alt que qualsevol altre edifici del poble.
The castle is taller than any other building in the village.
In this case, 'alt' is used to describe a high intensity of the sound.
Vaig sentir un so molt alt provinents de la ràdio.
I heard a very loud sound from the radio.
Here, 'alt' is metaphorical, referring to greatness or nobility of the ideals.