Adds a very basic perpetual background ambient hum. (#3150)

Content.Client/GameObjects/EntitySystems/AmbienceSystem.cs

@@ -0,0 +1,54 @@
+#nullable enable
+using Content.Shared.Audio;
+using JetBrains.Annotations;
+using Robust.Client.GameObjects;
+using Content.Shared;
+using Robust.Shared.Audio;
+using Robust.Shared.Configuration;
+using Robust.Shared.GameObjects;
+using Robust.Shared.IoC;
+using Robust.Shared.Prototypes;
+using Robust.Shared.Random;
+
+namespace Content.Client.GameObjects.EntitySystems
+{
+    [UsedImplicitly]
+    public class AmbienceSystem : EntitySystem
+    {
+        [Dependency] private readonly IPrototypeManager _prototypeManager = default!;
+        [Dependency] private readonly IRobustRandom _robustRandom = default!;
+        [Dependency] private readonly IConfigurationManager _configManager = default!;
+
+        private AudioSystem _audioSystem = default!;
+
+        private SoundCollectionPrototype _ambientCollection = default!;
+
+        private AudioParams _ambientParams = new(-10f, 1, "Master", 0, 0, AudioMixTarget.Stereo, true, 0f);
+
+        private IPlayingAudioStream? _ambientStream;
+
+        public override void Initialize()
+        {
+            base.Initialize();
+
+            _audioSystem = EntitySystemManager.GetEntitySystem<AudioSystem>();
+            _ambientCollection = _prototypeManager.Index<SoundCollectionPrototype>("AmbienceBase");
+            _configManager.OnValueChanged(CCVars.AmbienceBasicEnabled, HandleAmbience, true);
+        }
+
+        private void HandleAmbience(bool ambienceEnabled)
+        {
+            if (ambienceEnabled)
+            {
+                var file = _robustRandom.Pick(_ambientCollection.PickFiles);
+                _ambientStream = _audioSystem.Play(file, _ambientParams);
+            }
+            else if (_ambientStream != null)
+            {
+                _ambientStream.Stop();
+                _ambientStream = null;
+            }
+        }
+    }
+}
+