Apply the ringer volume to the join/hangup sounds with 15% minimum.

app/src/main/java/org/thoughtcrime/securesms/webrtc/audio/SignalAudioManager.java

@@ -79,7 +79,8 @@ public class SignalAudioManager {
       audioManager.setSpeakerphoneOn(false);
     }
 
-    soundPool.play(connectedSoundId, 1.0f, 1.0f, 0, 0, 1.0f);
+    float volume = ringVolumeWithMinimum(audioManager);
+    soundPool.play(connectedSoundId, volume, volume, 0, 0, 1.0f);
   }
 
   public void stop(boolean playDisconnected) {
@@ -89,11 +90,27 @@ public class SignalAudioManager {
     outgoingRinger.stop();
 
     if (playDisconnected) {
-      soundPool.play(disconnectedSoundId, 1.0f, 1.0f, 0, 0, 1.0f);
+      float volume = ringVolumeWithMinimum(audioManager);
+      soundPool.play(disconnectedSoundId, volume, volume, 0, 0, 1.0f);
     }
 
     audioManager.setMode(AudioManager.MODE_NORMAL);
 
     audioManagerCompat.abandonCallAudioFocus();
   }
+
+  private static float ringVolumeWithMinimum(@NonNull AudioManager audioManager) {
+    int   currentVolume = audioManager.getStreamVolume(AudioManager.STREAM_RING);
+    int   maxVolume     = audioManager.getStreamMaxVolume(AudioManager.STREAM_RING);
+    float volume        = logVolume(currentVolume, maxVolume);
+    float minVolume     = logVolume(15, 100);
+    return Math.max(volume, minVolume);
+  }
+
+  private static float logVolume(int volume, int maxVolume) {
+    if (maxVolume == 0 || volume > maxVolume) {
+      return 0.5f;
+    }
+    return (float) (1 - (Math.log(maxVolume + 1 - volume) / Math.log(maxVolume + 1)));
+  }
 }