My AirPods Pro 3 are experiencing the same issue. When I enable noise cancellation mode, my earbuds emit a sharp whistling sound while I'm chewing food, looking downward, or lying flat with my head tilted to one side. I returned them to the official store and purchased a new pair, but the same problem persists. As a user in China, I've found many others sharing identical experiences. Some users even reported that during flights, when attempting to activate noise cancellation, the whistling sound continued throughout the entire journey until the plane landed. This seems to indicate a potential flaw in the product design. I consulted with the Genius Bar staff, and they informed me that this issue might be improved through future firmware updates. However, they couldn't guarantee it. I've now decided to return the product and will temporarily refrain from purchasing AirPods Pro 3 until this problem is completely resolved.