Hello Carole Turner,
Noise cancellation works by countering the sound waves entering your AirPods Pro with neutralizing sound waves that in turn cancel most of the exterior noise. Because Active Noise Cancelation is controlled by your AirPods chip (H1 or H2), some noise will still reach your ears. For example, this year Apple improved the AirPods Pro's ANC with the 2nd version which they released in October, but they did not "perfect" the ANC feature.
If you really want to isolate yourself from distracting noise around you, I would suggest that you purchase construction grade noise mufflers that go in or over your ears.
Try playing some background music on your AirPods Pro as this usually drowns all excess sound that reaches the ear drums.
Also, check out this link:
If Active Noise Cancellation isn't working as expected on your AirPods Pro - Apple Support
I hope this helps. Have a nice day.