Distinguish loudness (loud/soft) and pitch (high/low) as two separate properties of sound.
Sounds can be different in two ways: how LOUD they are and how HIGH they are. Loudness is how big or soft a sound is -- a shout is loud, a whisper is soft. Pitch is how high or low a sound is -- a mouse squeak is high, a lion's roar is low.
Loud and high are not the same thing. A sound can be loud AND low, like a big drum, or soft AND high, like a tiny chime. This week you listen carefully for both properties in every sound you hear.
Mastery looks like: They correctly sort sounds by both loudness and pitch, and can explain that these are two separate properties.
Common stumbles: Treating loud and high as the same idea; only paying attention to one property at a time.