Here's what you might be thinking of:
* Purring: Cats purr when they're content, happy, or even when they're in pain. They might purr while you're petting them or while they're playing with a toy, which you might associate with them picking something up.
* Chirping: Sometimes cats make a chirping or trilling sound when they see birds or other small prey. This could be mistaken for a sound made while picking something up if it's associated with a cat looking at an object with interest.
* Hissing or growling: These sounds are defensive and are used to warn other animals or people to stay away. While they're not directly related to picking something up, they might occur if a cat feels threatened while handling an object.
It's important to remember that cats are very vocal animals and make a variety of sounds for different reasons. If you hear a sound you don't recognize, it's best to observe your cat's behavior and see if you can figure out what they're trying to communicate.