Sirens didn't go off in New Berlin for the test

[CycloneFan125]

So I went out to New Berlin today to get a recording of the T-128 at Gatewood Park. From what I know New Berlin tests every Thursday at 10:00 AM. So I arrive and 10:00 comes, nothing sounds 20 minutes later, nothing. I didn't hear any other sirens go off so I knew something was up. I was too impatient to stay longer as I was wasting over 20 minutes for nothing. Do they rotate and test particular sirens and the next time test another set of sirens?