silencend pellet trap

Hey all of you 😉
Like most of you, i shot my airguns in the backyard and have problems with the loud ,,impact sound “when the pellet hit`s the papercard. The trap itselfes is filled with some old cloth wich reduce the noise to a minimum. Last time i took a 60 cm. long plastiktube from around 40 cm in diameter and coverd the inside with old carpet and made some buffles extra wich all looke like the inside of a silencer now. Now i shoot to the middle of that construction an the pellet hit`s the papercard at the end of the tube with the result, that the impact sound is a bit quiter now.
But what´s about shooting in a longer tunnel( pipe from 1 or 2 meters)(which is added with a small LED light in the end) or an other construktion where the sound runs dead inside and you will here nothing outside in the garden???
Has anybody a idea or experience with other stuff???
(and yes,—excuse my english—please): Arrow