There are many reasons for the problem you are having:

1. The earpiece could possibly be faulty or even broken. It may need to be replaced.
2. The speaker might not be working properly and a new one would need to be installed.
3. If your phone as been in contact with water recently then there may be some water damage in the speaker.

For more help please visit the device's troubleshooting page:

Motorola Photon 4G Troubleshooting