I replaced my S4 LCD Screen, how do I get the sound working again?

Solutions for loudspeaker for Galaxy S4 I9505 no sound problem(from http://www.witrigs.com/replacement-parts...)

When external speaker for Galaxy S4 I9505 is broken, your phone doesn’t ring, sound notified or plays music/videos out. But if you plug the headphones in, everything comes back again. Bringing such a huge annoyance, it is speaker for Galaxy S4 not working that becomes a must solve problem.

Step 1. Check the setting

Go into the settings > sound > volume, make sure you didn’t turn on the vibration or silent switch, adjust the volume for music, ringtones and notifications, and then to hear if the Galaxy S4 no sound still.

Step 2. Reboot the phone

Hold on the power button and choose the restart option, hopefully do like this will eliminate any glitches causing the problem.

Step 3. Update software

For those who have not update OS, it will be a nice try. For others, you can find other ways to solve the problem of Galaxy S4 no sound.

Step 4. Replace loudspeaker

If all above the steps are failed, what you should consider is hardware problem and to replace a new speaker enclosure. If the trouble that speaker for Galaxy S4 not working still exists, send it to the repair center for checking the logic board.

Also, you should make sure if your USB board is installed well, because the loudspeaker is connected with it by two spring chips.