MAME source is you friend :
ROM_REGION( 0x80000, "gfx1", 0 )
ROM_LOAD( "b20-13.13", 0x00000, 0x80000, CRC(f6acdab1) SHA1(716b94ab3fa330ecf22df576f6a9f47a49c7554a) ) /* SCR tiles (8 x 8) */
ROM_REGION( 0x80000, "gfx2", 0 )
ROM_LOAD( "b20-14.72", 0x00000, 0x80000, CRC(89f889e5) SHA1(1592f6ce4fbb75e33d6ab957e5b90242a7a7a8c4) ) /* Sprites (16 x 16) */
ROM_REGION( 0x80000, "adpcm", 0 ) /* ADPCM samples */
ROM_LOAD( "b20-08.21", 0x00000, 0x80000, CRC(f3e19c64) SHA1(39d48645f776c9c2ade537d959ecc6f9dc6dfa1b) )
These are the three 4Mbit MASK ROM, the one containing ADPCM samples is the 'b20-08.21' one so download the set.
Do you have bad sound FXs or music or both?