The speaker sees himself as an old dog: bitter, worn down, and still unable to stop barking. That image carries a mix of anger and stubbornness. He knows he's past his prime, yet the noise keeps coming, almost like a habit he can't break.
The second stanza offers a bit of relief. Open fields pull him out of what he calls his "jealous office," a phrase that suggests work, or maybe a life of sitting indoors, that resents any freedom beyond its walls. The outdoors seems to be where he can breathe.
The last stanza turns darker and stranger. "A night at noon" is a contradiction, a darkness arriving in the middle of the day, and it is "calling" and "eating me up." Judging by the imagery, this could be dread, or the pull of death or despair. The mood is restless and uneasy: a grumpy, funny-sounding voice that slowly reveals something more frightening underneath.