You need to answer a given question containing a blank (_). Your answer must be one of the two objects mentioned in the question, for example "trophy" and "suitcase". Your answer must not contain a word that is not present in the question. Please don't use articles (e.g., the, a) before the answer.

The drifter pulled out his harmonica while riding the train and played a tune over the _ noise.
train

The sound of the speaker put a crack on the window close to it because the _ is too strong.
sound

Lily tried to clean the stain on a new carpet with a cleaner but failed, it seems the _ is tough.

stain