Final answer:
Obama is using volume modulation to emphasize the phrase "United States of America" in his speech.
Step-by-step explanation:
When Obama suddenly gets louder when he says the "United States of America," he's using volume modulation. Volume modulation is a technique used to emphasize certain words or phrases by adjusting the loudness of the voice.
Volume modulation can be used to create an impact and draw attention to important points in a speech. In this case, Obama is emphasizing the phrase "United States of America" by increasing the loudness, which can help to convey his pride and patriotism towards the country.
Other techniques like anaphora (repeating a phrase at the beginning of successive clauses) or climax (arranging words in increasing order of importance) are not being used in this specific example.