Think a dripping faucet is maddening? For Mariana, every noise is an annoyance and reminder of her despair.
In the third stanza, a night bird wakes her up ("she heard the night-fowl crow") (26). She doesn't go back to sleep. The next noise we hear is the crowing of the rooster, signaling daytime.
Then, the oxen start making noise and she realizes that, without "hope of change," every day would be like sleepwalking. And it isn't only outdoor noises that bother Mariana. In stanza six, the clock, the mouse in the wall, and the wind all serve to agitate her into despair. It is then that she starts to hear "old voices" calling to her from memory.
The final effect of all this noise imagery is that Tennyson's many noises may have finally driven her mad.