1. Different meanings

The human ear’s perception of the pitch of a sound is called pitch. Sometimes it also refers to the thickness, crispness or dullness of the sound. Generally speaking, "high" and "low" are used to describe it.

The human ear’s subjective perception of the strength of a sound is called loudness. Sometimes it also refers to the severity of the sound. Generally used to describe "big" and "small".

2. Different influencing factors

Tone is related to frequency. The greater the frequency, the higher the pitch. The speed at which an object vibrates, that is, the frequency at which the object vibrates, determines the pitch of the sound. The faster an object vibrates, the greater the frequency and the higher the pitch; the slower the object vibrates, the smaller the frequency and the lower the pitch.

Loudness is related to amplitude. The greater the amplitude, the greater the loudness. Loudness is also related to the distance of the sound emitter. The closer to the sound emitter, the louder the loudness; the further away from the sound emitter, the smaller the loudness.

3. Different propagation changes

During the propagation process of sound, the pitch is fixed.

As sound propagates, its loudness changes. The louder the sound becomes, the farther it travels.

Extended information:

Tone: There are "1, 2, 3, 4, 5, 6, 7 (Doremi Fa Solasi Duo)" in music, which refers to It's just that the pitch is getting higher and higher.

Loudness: refers to the strength of the sound. Usually people change the loudness by changing the volume. For example, mobile phone volume and TV volume.

The pitch of the sound frequency is one of the three main subjective attributes of the sound, namely volume (loudness), pitch, and timbre (also called timbre). Indicates the degree to which human hearing distinguishes the pitch of a sound.

Pitch is mainly determined by the frequency of the sound, but also related to the intensity of the sound. For a pure tone of a certain intensity, the pitch rises and falls with the frequency; for a pure tone of a certain frequency, the pitch of a low-frequency pure tone decreases as the sound intensity increases, but the pitch of a high-frequency pure tone rises as the intensity increases.

Reference: Baidu Encyclopedia - Loudness

Baidu Encyclopedia - Pitch