Voices on iMac when I log on; must restart to stop

Another reason I think the voice is some kind of reminder that has been inadvertently set is because it has happened at about the same time every night. And, the sound is always the same but is not like people talking on a radio....it's not 'real' talking...it is some kind of synthetic sound. I;m beginning to think this computer is sending me over the edge. LOL

A bunch of Apps were listed.....I don't know how they got there but, anyway, I did deselect the "play sound when receiving notifications." That could be it.! I'm being notified about everything on this new mac and it's driving me crazy. i have little banners in the corner of the screen and strange things happening. Deselecting these sounds may solve that problem and some others as well. Thanks so much. I will let you know if it works!.

This could be a blessing in disguise. I took most of the stuff out of notification center...both on my iPad and my iMac. I'm being notified of everything under the sun on both devices....I never thought about checking them out in System Prefs. Thank you so much! Now, If the strange voices do not appear tomorrow night, I will be in heaven!

So far, so good! No strange voices yesterday...I am hopeful that you solved the problem!

I spoke too soon.....the sound was back tonight. It was the same as always. I left it on for awhile and after the voices go on for a minute ot too, it changes to a sound not unlike static and stays that way until I restart. While the noise was on, I checked preferenes and apps to see if I could see anything obvious but couldn't.

There is just one thing and I cannot imagine how this is causing it but here is the story. When I first got my iMac a week ago I did not have the sound. After about the 4th day, I plugged in a new external disk. Since I did that, I have had the sound every night. I only hear it when I wake the computer up around 8pm...doesn't happen any other time of day. I noticed that I hear this noise at about the same time as the external disk does it's hourly back up to Time Machine. Tonight I checked the time. Time Machine had backed up at 8:02 and I came on about 8:05. While I have never actually checked the time each day it has been around 8pm. I have checked the Time Machine Preferences....they seem ok.

It really isn't something that especially bothers me in terms of operating the computer, but there is something definitely not right and I feel like I need to find and fix it as it could be indicative of some major problem with this new computer. Although, as I said, I did not have this sound until I got the new external disk and started backing up with Time Machine.

Any thoughts?

I called Apple (I have the extended warranty). The guy had never heard of such a thing. He put the thing on my computer that checks it out from his end. We went through a lot of tests; basically the same ones that you suggested. I did change a couple of settings. Then I reset PRAM. They are leaving the problem detector thing on and I have a case number. Whenever I get the sound again, I will call Apple and they will check it while it's happening. I asked him if he found anything suspicious and he said "I'm not sure." I will let you know if I find out anything.

Thank you all again. You were so helpful; I really appreciate it.

The two settings I turned off were: "Turn off Speakable Items" in Accessibility and "Notify of old backups" in Time Machine.

I just mentioned this to my daughter. She asked me if it sounded like a party line. Actually,it does.....like others talking on your telephone line. She says she gets that now and then from the wifi. Could that be the case here. I did not have wifi for my last iMac, I only had the iPad hooked up to it. But, this new iMac is now hooked up to wifi router. Knowing nothing about how wifi works, this idea seems plausible to me. It does sound like voices on a party line and it would explain the interference at particular times of day. Have you ever heard of this?

UPDATE: I have not had the voices since I talked to Apple and we changed the settings and reset PRAM as I wrote above. It has been about 5 or 6 days so I am hopeful that the problem is taken care of. I wrote down the settings we changed and, I think, one by one, I will change them back to see if I can determine what the culprit is. If I find out, I will post the results because it may help someone else.

Thanks to all of you for your help with this. I learned a lot about the computer from going through the trouble shooting with you. Apple users are so lucky to have this resource available. I have used it since 1998 and it has got me through 3 Macs, 1 iPod, and 1 iPad. Never would have made it with any of them without this discussion board.