mute de-amplify sound volume
Absolutely. Your internal speakers will have some nominal impedance, perhaps 8 ohms (you would need to do some research to know for sure). If you were to hook an 8 ohm resistor in parallel (across) the speaker, then half of the "volume" (power actually) would come out the speaker and the other half would simply be wasted as heat in the resistor.

Assuming the same 8ohm speaker, if the resistor were greater than 10 ohms, then less power would go to the resistor and the volume you hear would be louder.

As a practical matter you could try a few different resistors to see what works best for you. One thing to be aware of is that you need to use a resistor with an adequate power rating, perhaps 5 watts.

While it would be possible to compute the value of an "ideal" resistor, the mathematics is not as simple as you may think due to the way the human ear perceives sound. The perceived volume is not a linear relationship but rather a logarithmic function measured on the decibel scale.