Why is the decibel value unstable, and constantly varying? Is this normal?

Why is the decibel value unstable, and constantly varying? Is this normal?
2024-07-11 04:18:39 The decibel value measured by the sound level meter is the sound level of a short period of time (about hundreds of milliseconds), so the value is a instantaneous value. The sound level meter is measuring constantly, and at different times the sound is varing, so the decibel should be varing . This is normal.
Tonny12138
