Well sometimes this happens if the bit which is focussed  refreshes.
For example, when  I see items load into the system tray, but focus is on a desktop item, every time there is a new item in the tray, the desktop item is read again.
For example, when dropbox or google drive start it can take a while for their icon to appear in the tray, so if documents or computer is highlighted, it says it again each time the tray updates.
I notice it on windows 7 and ten, but do not have 8
On the other hand I do have a laptop running xp which when it shuts down has the falling tones of nvda twice.
The reason for that one eludes me.

So the answer for you is to discover why the desktop or whatever the item is, maybe the program window title, is refreshed more than once. some programs do this all the time, speed fan being a case in point. However not seen it on firefox  I've not tried the 64 bit version, but of course if the machine has toolbars and add ons in the browser its quite likely as each is initialised it repeats  much in  the same way as the  download library does if its open when a download is in progress.
Brian

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----- Original Message ----- From: "CJ" <cj@...>
To: <nvda@nvda.groups.io>
Sent: Friday, January 06, 2017 2:50 PM
Subject: [nvda] Repetition.

Hello,

after my old Windows 7 Machine gave up the ghost I had the fortune to
have a spare laptop to hand running on Windows 8.1. This seems to work
quite well apart from when I select a programme, say either Firefox or
Thunderbird. I can access these programmes well enough but for reasons I
do not fully understand when selecting say Thunderbird it will repeat
Thunderbird 4 times before shutting up and allowing me to start using
the selected option. I assume that I have made an error when setting
this machine up and am at a loss as to what setting is causing this
repetition problem. If anybody has experienced similar problems along
similar lines to my experience could somebody please advise me how they
rectified this problem or what I have got wrong? Any suggestions and
advice would be most welcome. Thank you, regards, CJ.