It is normal for a cat's chest to vibrate and make a low motor sound. This low motor sound has different meanings in different situations of the cat. For example, cats may make this sound when they feel relaxed and content. This can be seen as an expression of pleasure, similar to a human smile of contentment. In this situation, the cat will usually close its eyes, showing a state of enjoyment and peace of mind.

In addition, the low motor sound may also be the cat's performance when seeking attention or comfort. When cats feel uneasy or anxious, they may make this sound to attract their owner's attention in the hope of receiving care and comfort. In this case, owners can try to interact with the cats and pet them to relieve their tension.