Samsung DH40D User Manual page 180

Sound issue
There is an echo sound coming from the speakers.
Remote control issue
The remote control does not work.
Source device issue
A beeping sound is heard when my PC is booting.
Different decoding speeds between the product speakers and external speakers can cause an echo.
Speaker Settings to External.
In this case, set
Make sure that the batteries are correctly in place (+/-).
Check if the batteries are flat.
Check for power failure.
Make sure that the power cord is connected.
Check for any special lighting or neon signs switched on in the vicinity.
If a beeping sound is heard when your PC is booting, have your PC serviced.