Minimum Speaker Volume sets the minimum audio level the radio will produce when the volume knob is turned to its lowest position. This prevents the user from missing calls if they have turned the radio volume level too low and forgotten about it.
The CPS has a spin-box (shown above) which sets this level in increments of 1dB. The range for this value is model dependent and is:
-30 to +12 for high tier portables
-39 to +18 for high tier mobiles.
-52 to +9 for low tier portables
-1 to -47 for low tier mobiles
Setting Minimum Speaker Volume to Muted means that no audio will be produced when the volume knob is turned down. Muted is also the default value.