Final answer:
The words in brackets are a prepositional phrase. They start with a preposition ('by') and include the object of the preposition ('the baby crying so loudly'). The phrase as a whole functions within the sentence structure.
Step-by-step explanation:
The words in brackets - 'by the baby crying so loudly' - constitute a phrase known as a prepositional phrase. Prepositional phrases begin with a preposition ('by' in this case) and include the object of the preposition ('the baby crying so loudly'). On the other hand, a clause is a group of words containing a subject and predicate. While 'the baby crying so loudly' could potentially be seen as a clause, when used in this context with the preposition 'by', it functions as a prepositional phrase within the sentence structure.
Learn more about Prepositional Phrase