It seems that those haiku that have an inherently melodious quality are the most expressive and contain the most felt-depth. Robert Spiess
Experienced poets use a concentrated blend of sound and imagery to evoke an emotional response in readers. The effective use of sounds devices, such as alliteration, assonance, and consonance, can convey and reinforce the meaning, imagery, or experience of poetry, and the most important thing about using sound devices is that poets should not "call attention" to themselves by strained usage.
Below are the examples of haiku in which alliteration is effectively employed:
The life behind the one
I think I‘m living --
daylily pollen in wind
Marjorie Buettner's comment: ...The alliteration and rhythm of the first two lines complement the action evident in the third line. Both sections of this haiku reflect each other in a deep and resonate way. What is the life behind the one we think we are living? What a deeply felt introductory line which touches the heart immediately. The concluding third line completes the haiku with an image of resonating depth: daylily pollen in wind. It is not just any pollen but daylily pollen that blooms for only one day....
the swallow swoops
barely rippling the canal’s surface
-- perfect kill
Jared Stahl's Comment: The first line, “the swallow swoops,” is a great opener. The alliteration of the ‘SW’s’ works really well in helping to visualize the bird fly down to catch its prey....
hole in the stone wall
a perfect frame
Nathaniel B. Gach
Ruth Yarrow's Comment: The "aw" alliteration in "autumn afternoon" and the "oh" sounds in "hole in the stone wall" are a perfect frame for the feeling of appreciating beautify that pervades this haiku.