Answer: Quality is one of the characteristic of the sound which is not affected by the relative motion of an object.
Explanation: There are three characteristics of the sound which are pitch, loudness and quality.
Pitch depends on the frequency of the sound. The frequency varies in the case of the relative motion of the object.
Loudness depends on the amplitudes of the vibration. The amplitude also varies in the case of the relative motion of the object.
Quality is described by the word timber. The different sounds are produced by different sources. Therefore, It is not affected by the relative motion of the object.