second-generation noise

Refers to a giggly "imitation" racket dat a small child gleefully makes after hearing a grownup undertake a jarringly-loud activity, such as hammering, drilling, sawing, filing, etc.

Classic examples of "second-generation noise" would be if a youngster watches his parent or a visiting neighbor driving nails and then starts happily yodeling, "Bam-bam-bam-bam!" while pounding his fist on anything within reach around the house, or hollers, "ZzhEEEh-ukhkhahw, zzhEEEh-ukhkhahw, zzhEEEh-ukhkhahw, zzhEEEh-ukhkhahw..." (accompanied by vigorous back-and-forth motions with his forearm against various objects) after he witnesses someone raspingly slicing up boards or plywood with a crosscut saw.