No, not all cats raise both ears when they hear a sound. Cats have a remarkable ability to move their ears independently of each other, allowing them to locate the source of a sound more accurately. They can rotate their ears and move them in different directions to pinpoint the origin of a noise.
When a cat is attentive or trying to focus on a particular sound, it may raise one or both of its ears to better capture the auditory information. However, the exact ear movements can vary depending on the cat's breed, individual behavior, and the nature of the sound they are hearing. Some cats may raise both ears, while others may lift only one ear or even tilt their head to direct their ear towards the sound.
So, while it is common for cats to raise at least one ear when they hear a sound, it is not a strict rule that they will always raise both ears in response to auditory stimuli.