DIAGNOSIS: A faint, high-frequency buzzing or whine is usually coil whine from the internal power components. It's a common electronic phenomenon and generally not a sign of a defect.
FIX: First, confirm it's the camera and not another device. 1) Unplug the camera. Does the noise stop? If so, it's the camera. 2) Plug it into a different outlet, preferably on a different electrical circuit in your home. Sometimes "dirty" power or minor electrical interference from other devices on the same circuit can amplify the noise.
IF THAT DIDN'T WORK: The noise might be more noticeable in a very quiet room. If it's bothersome, try placing the camera slightly farther away or behind a small object (not blocking the lens or microphone) to dampen the sound. The noise doesn't affect the microphone's ability to pick up room audio.
HEADS UP: If the buzzing ever becomes loud, changes to a crackling sound, or you smell anything like overheating plastic, unplug the camera immediately and contact Blink support. That could indicate a faulty component. The normal coil whine should be very faint and constant.