About 50 years ago a Jew owned an old age home somewhere is chutz la'aretz. There was a certain gentile woman who used to say some words in a foreign language in her sleep that nobody there could understand. The doctors couldn't figure it out until they called this man to help them and he immediately identified what the woman was saying. She sang the words "תנו רבנן יאאאא" [The Rabbis taught, yeahhhhh] in a gemara niggun. They asked the woman about it and it turns out that her mother was a housekeeper for a Jewish family and when this woman was a baby of a year and a half her mother would take her along to work. She heard the man of the house learning gemara with this tune תנו רבנן יאאאאא and it became so entrenched in her memory she continued singing it many decades later.
[Heard from the Rebbe Shlita who heard it directly from the person involved]
From here we see the effect of what a child hears, even at a young age. It remains with the child forever.
May we always make sure our children always hear pure words and sounds.
