Soft is related to Tender. Tender is similar to Young. Young is the opposite of Elderly. Elderly is related to Old. 
Speech is related to Mouth. Mouth is related to Body. 
Soft <--RelatedTo--> Tender <--SimilarTo--> Young <--Antonym--> Elderly <--RelatedTo--> Old 
Speech <--RelatedTo--> Mouth <--RelatedTo--> Body 