Can anyone explain an error sound and erratic control of wireless mouse

Question

Hi people. I have a 21inch iMac from September 2013, just before Apple gave iMac a minor hardware update to the processor.
Within 9 months of  purchase i have had this weird problem.
The problem is the  "sound you get from the iMac when you press a key on the keyboard and its an error". Well... that error sound sometimes continues as if constantly pressing a key.
Even though I've just switched on the computer this sound occurs.
To add to that odd problem i have strange control over the wireless mighty mouse.
If i go to the task bar at the top of the screen and select the Apple icon and attempt to shut down or any selection for that matter, the cursor jumps from one selection to the other. And there are occasions when the Macintosh HD icon on the right of the desktop is highlighted in blue as if i have selected it.
Batteries in mouse are new Duracell and from the same new packet.

Answer 1

There are several possible causes for this issue. Please take each of the following steps that you haven't already tried until it's resolved. Some may not apply in your case.
1. Follow the instructions in this support article, and also this one, if applicable. A damaged or defective AC adapter could be the cause, even if it's the right kind.
2. Press down all four corners of the trackpad at once and release. If there's any effect, it's likely to be temporary, and in that case the unit must be serviced or replaced.
3. Open the Bluetooth preference pane in System Preferences and delete all pointing devices other than the trackpad, if applicable. Disconnect any USB pointing devices. By a "pointing device," I mean a peripheral that moves the cursor, such as a trackpad, mouse, trackball, or graphics tablet. A plain keyboard is not a pointing device.
4. Start up in safe mode and test, preferably without launching any third-party applications. If you don't have the problem in safe mode, but it comes back when you restart as usual, stop here and post your results. Do the same if you can't start in safe mode. If there was no difference in safe mode, go on to the next step.
5. Reset the System Management Controller.
6. If you're using a Bluetooth trackpad or mouse, investigate potential sources of interference, including USB 3 devices.
7. A swollen battery in a portable computer can impinge on the trackpad from below and cause erratic behavior. If you have trouble clicking the trackpad, this is likely the reason. The battery must be replaced without delay.
8. There's a report that a (possibly defective) Thunderbolt Ethernet adapter can cause the built-in trackpad of a MacBook to behave erratically. If you're using such an adapter, disconnect it and test.
9. There's also a report of erratic cursor movements caused by an external display that was connected but not turned on.
10. If none of the above applies, or if you have another reason to think that your computer is being remotely controlled, remove it from the network by turning off Wi-Fi (or your Wi-Fi access point), disconnecting from a Bluetooth network link, and unplugging the Ethernet cable or USB modem, whichever is applicable. If the cursor movements stop at once, you should suspect an intrusion.
11. Make a "Genius" appointment at an Apple Store to have the machine and/or external trackpad tested.