Strange noises emitted by plumbing after toilet is flushed

Hello, I have a Toto Promenade toilet. Whenever the toilet is flushed, a relatively loud whirring noise occurs which gets increasingly higher in pitch until the noise ceases. This lasts for less than 10 seconds, and sounds like it is coming from the plumbing below the floor of the toilet. Would anyone happen to know what might be wrong with my plumbing? This plumbing and toilet are new in my remodeled home (less than 2 years old).

First make sure that the water supply at the wall is open all the way.

That did the trick!

Terry, thank you very much for your prompt reply and advice. Your recommendation fixed our problem! Apologies for the lengthy delay in replying, but I had to wait for my husband to get back from a trip.

Read the title too fast and I thought it read:
Strange noises emitted by plumber after toilet is flushed