Just to make sure everyone knows what settings you need for REW and a USB microphone without a loopback timing reference:


In REW Preferences:

Click image for larger version.  Name: Screen Shot 2021-02-05 at 11.46.42.png  Views: 260  Size: 175.4 KB  ID: 15243




In the Measurement window:

Click image for larger version.  Name: Screen Shot 2021-02-05 at 11.44.29.jpg  Views: 203  Size: 129.5 KB  ID: 15242