* First of all, a huge CREDITS and tons of thanks to Gtj94 from XDA on finding this solution. 
* Note, this workaround are suitable with SENSE & AOSP rom (especially Gingerbread based). 
* Give personal feedback after this. Want to know feedback from others too. 
* FOR ROOT USER ONLY

Step 1:
Using Wi-Fi or Mobile Data, download an app called 'gscript lite' (without quote) from Market.

Step 2:
Once finish, open the app. Then, tap Menu and tap Add Script.

Step 3:
- In the 'Name' section, just type any name you want (I.E, i name it 'Sound Booster').
- In 'Script' section , got 'Need SU (stand for SuperUser)?' check-box, just tick it.
- In the blank box, type the code:
  a) For SENSE rom = snd3254<space>-dspmode<space>07 for better speaker quality and snd3254<space>-dspmode<space> 11 for better headset quality.
  b) For CM7 and MIUI = snd3254<space>-dspmode<space>04' for better speaker quality and snd3254<space>-dspmode<space>08 for better headset quality.

Step 4:
After finish, long-press at the script we create just now and tap Run. If got SuperUser pop-up, just allow it.

THEN YOU CAN TEST WHETHER THE CODE BOOST YOUR SPEAKER AND HEADPHONE SOUND OR NOT.     

* First of all, a huge CREDITS and tons of thanks to Gtj94 from XDA on finding this solution.
* Note, this workaround are suitable with SENSE & AOSP rom (especially Gingerbread based).
* Give personal feedback after this. Want to know feedback from others too.
* FOR ROOT USER ONLY

Step 1:
Using Wi-Fi or Mobile Data, download an app called 'terminal emulator' (without quote) from Market.

Step 2:
- Run the app and the script below.
  a) 'su' (without quote) and press enter.
  b) 'snd3254 -dspmode xx' (without quote) and press enter.

THEN YOU CAN TEST WHETHER THE CODE BOOST YOUR SPEAKER AND HEADPHONE SOUND OR NOT.     

Code: 'snd3254 -dspmode xx' (xx need to be replace with numbers from table)

01. Original_Phone_Rec
02. Original_Phone_Spk
03. Original_Phone
04. Original_Spk
05. Dolby_a_spk
06. Dolby_a_hp
07. Dolby_v_spk
08. Dolby_v_hp
09. Srs_a_hp
10. Srs _a_spk
11. Srs_v_hp
12. Srs_v_spk
13. Bass Booster
14. Blues
15. Classical
16. Country
17. Jazz
18. Latin
19. New Age
20. Piano
21. Pop
22. R&B
23. Rock
24. Treble Booster
25. Vocal Booster

# The above table is for SENSE Gingerbread rom.
# If you notice at the table, spk = speaker & hp = headphone
# Table number 13 to 25 only for headphone sound only, not speaker.
# For CM7 and MIUI, you can refer the code here. --> Click Here