Answer:
B. 100%
Step-by-step explanation:
When the amplitude of a vibrating membrane increases the loudness of sound increases. Higher amplitude waves will mean more energy and greater intensity which causes the sound to be louder.
Loudness is proportional to the square of the amplitude. This will simply mean when the amplitude of a wave is doubled, the sound will be 4 times louder.
In this case, 50% increase in the amplitude of a vibrating membrane will cause a 100% increase in the loudness of sound.