This can be related to the way the game plays back sound through the PC itself. If the PC is set to Surround Sound in the settings, but the device it's plugged in to does not support surround sound, the voices will not be heard and many or some sounds will not play correctly.
Please follow these steps in order to set the PC to Stereo sound:
1. Open the Start Menu.
This article documents the common and notorious glitches that you are likely to encounter when playing the game of KOTOR. For Glitches concerning KOTOR II, please read that game's glitch page rather than this one. It is not an exhaustive list of every anomaly that may possibly occur. There are numerous minor animation oddities and graphical surprises that you can uncover if you try to trigger. Knights of the Old Republic 2: The Sith Lords was released in 2004, one year after the release of the original game, Knights of the Old Republic. It received positive reviews after it’s release although the game was left unfinished as LucasArts forced the developers, Obsidian, to finish the game within 16 months.
3. Choose Hardware and Sound.
5. Select the correct audio device and ensure it is set as the default.
6. With the device still selected, click Properties.
7. On the Advanced tab, ensure the Default Format is set correctly for your device. Typically, this will be '2 channel, 16 bit, 44100 Hz (CD Quality)' or '2 channel, 16 bit, 48000 Hz (DVD Quality)' setting. Click OK to apply these settings.
8. With the device still selected, click Configure.
9a. Ensure the Audio Channels is set to Stereo and click the Test button. You'll hear sounds play across your left and right speakers.
9b. If you select another setting here, such at 5.1 Surround sound, and click Test, but do not hear sound across all of your speakers, then the sound card or speakers you have do not support this audio channel type or are not plugged in correctly.
10. Click Next to continue through this Speaker Setup window until you receive a Finish button.
11. Click OK to save these settings and close the window.
Windows 8
1. From Desktop View, hold the Windows key on your keyboard and hit C on the keyboard as well.
3. Choose Hardware and Sound.
Kotor 2 No Sound Effects
5. Select the correct audio device and ensure it is set as the default.
6. With the device still selected, click Properties.
7. On the Advanced tab, ensure the Default Format is set correctly for your device. Typically, this will be '2 channel, 16 bit, 44100 Hz (CD Quality)' or '2 channel, 16 bit, 48000 Hz (DVD Quality)' setting. Click OK to apply these settings.
8. With the device still selected, click Configure.
9a. Ensure the Audio Channels is set to Stereo and click the Test button. You'll hear sounds play across your left and right speakers.
9b. If you select another setting here, such at 5.1 Surround sound, and click Test, but do not hear sound across all of your speakers, then the sound card or speakers you have do not support this audio channel type or are not plugged in correctly.
10. Click Next to continue through this Speaker Setup window until you receive a Finish button.
Kotor 2 No Sound Effect
11. Click OK to save these settings and close the window.
Kotor 2 Cutscene No Sound
If the sound plays correctly now in the game, then you may need to review your computer or speaker setup before trying to enable surround sound again.