and a pop at the end from the speaker.
It will do that if the sample stops not at the zero voltage level. Try the fade out function on Audacity to edit your files.
Alternately it could be produced by the player's amplifier turning off after playing.
I should mention the static is there regardless how low/high the volume knob gets turned.
I have herd people describe audio artifacts as static but I don't think that is right. Static is basically white noise. More than likely you here clicks and distortions in the file. If you can look at the output signal with an oscilloscope and that would tell you, but I don't suppose you have one.
Often sounds are distorted by clipping, that is the signal flat lines at the top and bottom. To stop this from happening you need to reduce the peak amplitude of the audio file. Again using Audacity you can "normalise" the waveform, a good value to normalise to is about 13dBs down.