Quality also has to do with how pleasing the sound is to your ear. An inexperienced music student will produce a lower quality sound than an experienced student. Quality also depends on the number of harmonics that make up a sound and their relative loudness. The fundamental frequency is the first harmonic of a note. Harmonics are also called overtones, which are notes that are multiples of the original tone.
Intensity depends on the strength of a vibration producing a sound.
It has nothing to do with pitch. The stronger vibration compresses the molecules of the air more forcefully and gives them more energy. The stronger the vibration, the higher the intensity. When strong compression waves reach your ear, it interprets it as a loud tone. The distance at which sound can be heard also depends on intensity.