The Cramér-Rao Bound (CRB) for direction of arrival (DOA) estimation has been extensively studied over the past four decades. with a plethora of CRB expressions reported for various parametric models. In the literature. there are different methods to derive a closed-form CRB expression. https://www.roneverhart.com/Western-Digital-Ultrastar-DC-HC550-WUH721816ALE6L0-0F38460-16TB-7-2K-RPM-SATA-6Gb-s-512e-ISE-3-5in-Hard-Drive/