amplify — If you amplify a sound, you make it louder, usually by using electronic equipment.
enlarge — Make or become bigger or more extensive.
grow — to increase by natural development, as any living organism or part by assimilation of nutriment; increase in size or substance.
increase — to make greater, as in number, size, strength, or quality; augment; add to: to increase taxes.
lengthen — to make longer; make greater in length.
stretch — to draw out or extend (oneself, a body, limbs, wings, etc.) to the full length or extent (often followed by out): to stretch oneself out on the ground.
