If you are seeing video but not hearing audio when using the Brainshark app on an Apple iOS device (iPad, iPhone, iTouch), please check the sound settings for your device.
To deactivate the mute function, double-tap the Home button to open up the multi-task bar. You will see the option to control the volume meter, ensure this is not all the way down (muted). Alternatively, this can be changed using the physical volume buttons on the side of the device.
For the iPhone:
Make sure the device is not in vibrate only mode using the switch on the side of the device. Swipe up from the bottom of the device to make sure the volume level is turned up and is not muted. Alternatively, this can be done using the physical volume buttons on the side of the device.