diff --git a/APU.cpp b/APU.cpp
index 37714ab..4ed3d23 100644
--- a/APU.cpp
+++ b/APU.cpp
@@ -79,11 +79,21 @@ namespace APU
         }
     }
 
-   void init()
+    void silence()
+    {
+        SDL_PauseAudioDevice(sdlAudioDevice, 1);
+    }
+
+    void resume()
+    {
+        SDL_PauseAudioDevice(sdlAudioDevice, 0);
+    }
+
+    void init()
     {
         SDL_AudioSpec audioSpec{11025, AUDIO_U8, 1, 0, AUDIO_BUFFER_SIZE>>2, 0, 0, &audioCallback, NULL};
         sdlAudioDevice = SDL_OpenAudioDevice(NULL, 0, &audioSpec, NULL, 0);
-        SDL_PauseAudioDevice(sdlAudioDevice, 0);
+        resume();
         //samples_time=SDL_GetTicks();
     }
 
@@ -183,11 +193,11 @@ namespace APU
         DIVAPU_envelope_sweep++;
         if (DIVAPU_envelope_sweep==8) {
             DIVAPU_envelope_sweep=0;
-            if ( NR12&0x7 ) {   // If sweep pace != 0, envelope sweep is enabled
+            if ( CH1.enabled && (NR12&0x7) ) {   // If sweep pace != 0, envelope sweep is enabled
                 CH1.envelope_sweep_timer++;
                 if ( CH1.envelope_sweep_timer == (NR12&0x07) ) {    // if timer == envelope sweep, increase or decrease volume
                     CH1.envelope_sweep_timer=0;
-                    if (NR12&0x80) {    // bit set increases, reset decreases
+                    if (NR12&0x8) {    // bit set increases, reset decreases
                         if (CH1.volume<0x0f) CH1.volume++;
                     } else {
                         if (CH1.volume>0) CH1.volume--;
diff --git a/APU.h b/APU.h
index fbad62c..b680916 100644
--- a/APU.h
+++ b/APU.h
@@ -8,6 +8,8 @@ namespace APU
 
     void init();
     void reset();
+    void silence();
+    void resume();
     void incDIVAPU();
     void update(uint32_t dt);
 }
diff --git a/Makefile b/Makefile
index 56f73da..722780c 100644
--- a/Makefile
+++ b/Makefile
@@ -2,10 +2,10 @@ compile:
 	g++ -g *.cpp -lSDL2 -o gb
 
 run: compile
-	./gb
+	./gb tetris.gb
 
 debug: compile
-	gdb --args gb supermarioland.gb
+	gdb --args gb tetris.gb
 
 debug1: compile
 	gdb -ex run gb
diff --git a/debug.cpp b/debug.cpp
index 3b0018e..b63d5c5 100644
--- a/debug.cpp
+++ b/debug.cpp
@@ -3,6 +3,7 @@
 #include "sm83.h"
 #include "sm83dis.h"
 #include "mem.h"
+#include "APU.h"
 //#include "z80analyze.h"
 #include "ui.h"
 #include "ui_window.h"
@@ -348,7 +349,7 @@ namespace debug
 
     void pause()
     {
-        //zx_ula::sound_disable();
+        APU::silence();
         is_paused = true;
         breakpoints[sm83::getPC()] &= ~8;
     }
@@ -369,7 +370,7 @@ namespace debug
         is_debugging = is_paused = false;
         refresh();
         gbscreen::focus();
-        //zx_ula::sound_enable();
+        APU::resume();
     }
     
     const bool debugging() { return is_debugging; }