Add FAQ on EchoCancellation (#33)

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* code

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docs/faq.md

@@ -1,3 +1,26 @@
 ## Demo does not work when deploying to the cloud
 
-Make sure you are using a TURN server. See [deployment](/deployment).
+Make sure you are using a TURN server. See [deployment](/deployment).
+
+## Recorded input audio sounds muffled during output audio playback
+
+By default, the microphone is [configured](https://github.com/freddyaboulton/gradio-webrtc/blob/903f1f70bd586f638ad3b5a3940c7a8ec70ad1f5/backend/gradio_webrtc/webrtc.py#L575) to do echoCancellation.
+This is what's causing the recorded audio to sound muffled when the streamed audio starts playing.
+You can disable this via the `track_constraints` (see [advanced configuration](./advanced-configuration])) with the following code:
+
+```python
+	audio = WebRTC(
+		label="Stream",
+		track_constraints={
+                "echoCancellation": False,
+                "noiseSuppression": {"exact": True},
+                "autoGainControl": {"exact": True},
+                "sampleRate": {"ideal": 24000},
+                "sampleSize": {"ideal": 16},
+                "channelCount": {"exact": 1},
+            },
+		rtc_configuration=None,
+		mode="send-receive",
+		modality="audio",
+	)
+```