Matthew Arnold uses sound in two ways in "Dover Beach." The first is use of sound-related figures of speech, such as alliteration, assonance, and onomatopoeia. The second is his description of the sound of the waves.
In the first stanza we have a sequence of sounds that give the impression of the eternal cycle of the waves, with the tide ebbing and rising day after day. We see this effect in the first stanza in the word sequence: " ...grating roar ...waves draw ... cadence slow."
Next, Arnold also has extensive descriptions of the sounds of the waves and the pebbles on the shore in the poem. The terms in which the sound is described create meaning through a form of personification, or attribution of human qualities of emotion to inanimate objects. The sound of the waves is a "grating roar" and the waves "fling" pebbles, both impressing upon us the strength of the tides. However, despite this power, the sound is also a "tremulous cadence," which suggests perhaps the hymns and chanting of a religious service. This emphasizes that religion, which is at high tide, despite its visibility, is gradually withdrawing from the world in the modern era.
In "Dover Beach," sound is a central element. Arnold uses much imagery of sound as well as rhythm to great effect in this famous poem. Let's look at some lines to examine some of these.
In the first verse, Arnold uses personification:
Listen! you hear the grating roarOf pebbles which the waves draw back, and fling, (9-10)
Begin, and cease, and then again begin, (12)
With tremulous cadence slow, and bringThe eternal note of sadness in (13-14).
Sophocles long agoHeard it on the Ægean, and it broughtInto his mind the turbid ebb and flowOf human misery; weFind also in the sound a thought,Hearing it by this distant northern sea (15-20).
But now I only hearIts melancholy, long, withdrawing roar,Retreating, to the breathOf the night-wind, down the vast edges drearAnd naked shingles of the world (24-28).
Swept with confused alarms of struggle and flight,Where ignorant armies clash by night (36-37).