Don't play random noise on startup

src/sound.cpp

@@ -59,6 +59,7 @@ void Sound::init() {
     i2s_driver_install(i2s_num, &i2s_config, 0, NULL);
     i2s_set_pin(i2s_num, &pin_config);
 
+    /* play a sine wave (example code) */
     triangle_float = -32767;
 
     for(i = 0; i < SAMPLE_PER_CYCLE; i++) {
@@ -76,6 +77,8 @@ void Sound::init() {
  
         i2s_push_sample(i2s_num, (char *)&sample_val, portMAX_DELAY);
     }
+
+    stop();
 }
 
 void Sound::play() {