If doing well will grow roughly one foot per year. Will never, however block noise no matter how healthy.

It is too bad you chose this coarse-textured weed over various attractive hedges like Pacific wax myrtle.

I had read that they DO help with sound blocking once they get huge, if this doesn't (as dense as they get), what does?

I think they look nice when they have tons of space to spread, shiny green leaves, so to each his own I guess...

There are many in my neighborhood and I've never had "starters" show up on my 1 acre so I don't know if there are slightly different varieties within "english laurel" but I've not had a problem with seeds.

Sprouting of seedlings in this area frequent. Multiple local sites have conspicuous infestations, with ivy, holly, cotoneasters etc. also often present as well

"Purplish-black cherry-like fruit ripens in the late summer or fall; birds eat these and deposit the pits everywhere. Shade tolerant, English Laurel is weedy in our wooded parks, where some specimens are more than 40' tall, wider still"

--A.L. Jacobson, WILD PLANTS OF GREATER SEATTLE - SECOND EDITION

Vegetation does little to block noise. It doesn't matter what kind of plant. You need something like the concrete walls along the freeway to get a marked improvement.

The seeding of this plant is so common in our area that the King County Noxious Weed Board has included English laurel (as well as English holly and Mountain ash) in its 2009 listings as "weeds of concern". This is to alert gardeners of their invasive potential and encourage them to make other, better choices. In my Shoreline garden, I grow none of them but I am constantly pulling out seedlings of all three - holly and laurel being the most prolific. I occasionally have English ivy seeding in as well. Birds are most generous and very liberal when distributing these 'gifts'.

And bboy is correct. No vegetation, regardless of height or thickness makes an effective sound barrier. You need a substantial solid structure to accomplish that.

Removing the ivy etc. from public lands in Seattle over a 20 year period has been estimated to cost 52 million dollars.