Seamus Heaney - use of sound

Heaney is known for using sound as a major literary device in his poetry. In Mid-Term Break, he talks about "counting bells nelling classes to a close", and the alliteration of the "c" gives the line a beat, just as a funeral bell has a steady beat.
Then the letter "c" is repeated in the next stanzas - his father is "crying", and the baby "cooing". All three sounds are linked by the "c", so that the alliteration stands out when the poem is read, and the reader connects them in his/her mind. Later, we have consonance of the letter "s" which is a quiet, shushing sound. The bedside is "soothed" and peaceful.
In Digging we have a "clean rasping sound", and the "squelch and slap", the "curt cuts" in which he uses alliteration to suggest the sound the spade makes as it goes through the earth.
Then you have Death of a Naturalist and all the delicate sounds of a childhood Spring day, followed by the ugly "coarse croaking" and the "slap and plop" of summer, and the day the frogs were mating.
If I was going to concentrate on the use of sound in poems, I'd compare any one of these poems with The Field-Mouse because Clarke uses sound in her poem too. The long grass is a "snare drum", and the air "hums" with jets, it's "stammering with gunfire".
She also uses metaphors of fighting and physical damage, "wounding my land" and the field "lies bleeding", and so does Heaney in Death of a Naturalist.