setVolume

I set up 3 buttons for the sound, they are 100(loud), 75, and 0(mute). When I run the movie, it was working fine at the first time when I press the mute button. After that, while I am reviewing my other pages, the sound comes back, and the mute button still on. Below is the code, please help, thank you in advance.

var my_sound = new Sound();

my_sound.loadSound( “music/night.mp3”, true );
my_sound.onSoundComplete = function() {
my_sound.loadSound( “music/night.mp3”, true );
};

b_1.enabled = 0;
b_1.gotoAndStop( “disabled” );

b_1.onRelease = function(){
reset_sound_buttons();
this.gotoAndStop( “disabled” );
this.enabled = 0;
my_sound.setVolume( 75 );
};

b_2.onRelease = function(){
reset_sound_buttons();
this.gotoAndStop( “disabled” );
this.enabled = 0;
my_sound.setVolume( 100 );
};

b_mute.onRelease = function(){
reset_sound_buttons();
this.gotoAndStop( “disabled” );
this.enabled = 0;
my_sound.setVolume( 0 );
};

reset_sound_buttons = function() {
b_1.enabled = 1;
b_1.gotoAndStop( “_up” );
b_2.enabled = 1;
b_2.gotoAndStop( “_up” );
b_mute.enabled = 1;
b_mute.gotoAndStop( “_up” );
};
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