Heaney uses onomatopoeia most in "Churning Day" because it is a very noisy process, almost never in "Mid-Term Break" because it is a sombre poem where the atmosphere is too sad for noise, and a little bit in "An Advancement of Learning" to deepen our understanding his fear of rats. Whenever Heaney wants to make sounds clearer to us he uses onomatopoeia.
Heaney uses texture and touch as well to convey to us in greater detail how it would feel if we were there and touched things. In "Churning Day", Heaney starts by describing how the crust was "coarse-grained" (Line 1) making us realise how rough it was, this reflects the mood of the poem in general, how hard "Churning Day" was. Heaney describes how the kitchen floor was "flagged" (Line 9) to describe how flat the floor was. We then get into the real action of the poem, "Arms ached. Hands blistered."(Lines 15-16) This describes how it felt to do all this churning, it was not an easy thing to do. "Corrugated butter-spades" (Line 21), describes how these butter-spades were wrinkled. "Printed slabs" (Line 30) is Heaney's last use of touch in "Churning Day", to describe how they had been finished totally now and felt professional. In contrast, in "Mid-Term Break", there is hardly any use of the sense of touch apart from "stanched and bandaged" (Line 15) to describe how the corpse looked and felt. Heaney again is much more interested in the deeper emotions than materialistic things in this poem. In "An Advancement of Learning", Heaney uses a lot of texture to describe how it would feel to touch the rat. "Dirty-keeled swans" (Line 8) describes how the river was dirty again. This is all an introduction to show that there is no surprise, as this is a dirty place, that rats are living here. "Slimed" (Line 11) describes how the rat felt slimy and dirty (or how he imagined it would feel if he touched it). This is a use of sibilants ("s" sounds to make the poem feel uneasy).