The whiny noise is caused by the Avago 3360 sensor and other internal components, it does not have an impact on the mouse's performance. The issue has been fixed and future products will not suffer from this problem. Users who have a faulty mouse can request a replacement via BenQ's service center.
[S]ince customer comfort and satisfaction are important to BenQ, the company is offering replacement mice starting mid-March. EC-B mice owners who suffer from the noise issue can contact BenQ's service center directly for further assistance.