I am hearing a chatter coming from the engine compartment, what could it be?

What is your question?

I thought it might be spark knock, but it happens when I am driving at steady speeds. It seems most apparent when at speeds higher than 40 mph. I bought this vehicle used with about 30k miles and it now has 41k.

How long has your 2014 Toyota Highlander had this problem?

It has been going on for a few months, but getting worse.