No chimes after NVRAM and PRAM reset

I was having some startup issues so I reset the NVRAM on my 27" iMac (Mid 2011) running OS X 10.11.4 and then had to restore from my Time Machine Backup. The procedure worked just fine. The computer boots faster and I'm not having the "Your Computer restarted because of a problem" dialog box. But, I now no longer have the chimes when I start the computer and I miss hearing them. I had the same thing happen on my G4 MDD running OS X 10.5.8 when I had a startup problem. How do I restore the chimes?