diff --git a/zx_ula.cpp b/zx_ula.cpp
index 877f12b..5b3d25b 100644
--- a/zx_ula.cpp
+++ b/zx_ula.cpp
@@ -202,8 +202,8 @@ namespace zx_ula
     void port_out(int port, int val)
     {
         border_color = val & 0x7;
-        mic = (val&0x08)==0;
-        ear = val&0x10;
+        mic = (val&0x08)?0:1;
+        ear = val&0x10?1:0;
         //printf("EAR:%i MIC:%i\n", ear, mic);
     }
 
@@ -264,8 +264,8 @@ namespace zx_ula
     void sound_update(const uint8_t dt)
     {
         t_sound += dt;
-        if (t_sound>=318) {
-            t_sound-=318;
+        if (t_sound>=316) {
+            t_sound-=316;
             //sound_pos = (sound_pos+1) & 0x3ff;
             //sound_buffer[sound_pos] = ear*128;
 
@@ -274,10 +274,12 @@ namespace zx_ula
                 sound_buffer[sound_pos++] = ear*128;
                 if (ear) last_1 = sound_pos;
             }
-            /*else
+            else
             {
-                printf("WARNING! Sound buffer overflow!\n");
-            }*/
+                //for now, drop then buffer
+                sound_pos = last_1 = 0;
+                //printf("WARNING! Sound buffer overflow!\n");
+            }
         }
     }
 }
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