Loudness refers to the perception of sound intensity or volume. It is how we perceive a sound as being either soft or loud.
Pitch refers to how high or low a sound is perceived to be. It is determined by the frequency of a sound wave.
Decibel (dB): Decibel is a unit used to measure the intensity or loudness of a sound.
Timbre describes the quality or character of a sound that distinguishes it from other sounds, even when they have the same pitch and loudness.