Adjust the relative volume level using the voice-volume CSS property.
The following is the syntax:
voice-volume: [x-soft | soft | medium | loud | x-loud]
The following is a code snippet for the voice-volume speech media property:
p { voice-volume: soft; }
You can also set the volume in decibals
p { voice-volume: 2dB; }
Set both the voice-volume media property and volume level in decibals :
p { voice-volume: medium 3dB; }