Voice is related to Hear. Hear is related to Activity. Aid is a type of Activity. Hand is a type of Aid. 
Device is related to Leaf. Leaf is related to Fall. Fall is the opposite of Increase. Swell is a type of Increase. 
Voice <--RelatedTo--> Hear <--RelatedTo--> Activity <--IsA-- Aid <--IsA-- Hand 
Device <--RelatedTo--> Leaf <--RelatedTo--> Fall <--Antonym--> Increase <--IsA-- Swell 