A new sharpness algorithm has been proposed for improved integrity and human auditory perception, considering the complete sound transfer functions of the concha, middle ear, and inner ear. A new algorithm-based design procedure has been employed to evaluate the sharpness of a direct injection diesel engine noise. Normal components of the vibration velocities of the engine block surface were calculated using flexible multi-body dynamic analysis, verified by the engine bench tests and then extracted to simulate the structural radiated noise via standard boundary element codes. The acoustic response results revealed that considerable sound power levels existed in the main frequency ranges of 1550–1900 Hz and 2350–2800 Hz. After the engine block was modified and bench-tested, it was found that the sharpness of the measured engine noise was reduced by 6.47%. This has validated the new algorithm and the new algorithm-based design procedure which made the engine sound lower-pitched.