Answer: one that makes a more mellow sound
Explanation:
One that makes a more mellow sound will have a constant frequency than the one that has a loud sound.
Fading away of sound waves depends on the wavelength of the sound. The one that has a loud sound with high frequency will have a brighter sound. While the more mellow one will have the bassier sound. Therefore, the sound with a more mellow sound will fade away faster.