Osmond, 57, underwent surgery on Tuesday in Boston to treat a hemorrhagic polyp (otherwise known as a bleeding lesion) on his right vocal cord. The operation was performed by Harvard Medical School's Dr. Steven M. Zeitels, who recently treated Grammy winner Sam Smith, as well as Adele and John Mayer.
"[Dr. Zeitels] showed me the operation on video. Got some cool pictures," Osmond tells PEOPLE via email. "It took an hour to complete the procedure at Massachusetts General Hospital. Now, it's pure silence for three weeks. Not even a whisper or whistle."
The performer writes that he'll begin rehab on Sept. 1 and is expected to be singing again in time for his Sept. 29 performance in Las Vegas with sister Marie.
Osmond explains his polyp didn't develop from singing incorrectly.
"This is a common misconception. Opera singers get this. It's just the fact that I use my instrument a lot," Osmond writes. "[Dr. Zeitels] showed me the documentary [National Geographic: Incredible Human Machine] he did with Steven Tyler, who had the same thing I did. The before and after pictures were almost exactly like mine."
The star, who calls Zeitels a "genius," will have to be silent for three weeks while he recovers.
Osmond posted a hospital picture on Tuesday before the procedure, telling Facebook fans that he was "excited."
"I'm certainly going to have a lot of time on my hands to read the comments that you post," he wrote of his forced silence. "I can hardly wait to hear what you have to say."
Osmond also Tweeted about his recovery, sharing, "I won't lie. It's really tough. But I use my smartphone to communicate. I have this text-to-speech app that helps me."
Because I must be silent for 3 wks after vocal surgery, It's funny how many people are posting on my FB, shhhh, be quiet and shut up Donny"— Donny Osmond (@donnyosmond) August 12, 2015
I won't lie. It's really tough. But I use my smartphone to communicate. I have this text-to-speech app that helps me https://t.co/uhwrxGG1gS— Donny Osmond (@donnyosmond) August 12, 2015
Keeping Osmond's spirits up is some happy family news – the singer just became a grandfather again on Saturday. The new addition was born on 8/8, weighing in at 8 lbs. and is Osmond's eighth grandchild. "I think they should name him Octavio," he jokes to PEOPLE.
With the baby born in Austin, Texas, "I now have a bonafide cowboy in my family," Osmond writes. "I guess now I really am a little bit country and not just a little bit rock 'n' roll!"
Reporting by SARAH MICHAUD