If you have a full inventory, picking up a stacked item entity won't make a sound if it's not fully picked up.
For example, if I have 63 torches and there's a stack of 2 torches on the ground there will be no sound when picking one torch up. If I have 62 torches there will be a sound because the stack is fully picked up.
Linked issues
testing discovered 1
Comments 2
Resolved in favor of MC-120643, this issue is included there now.
Can confirm for MC 1.12.1.