diff --git a/dialogflow/analyze_content_stream_test.py b/dialogflow/analyze_content_stream_test.py
index 29aa40b0fa1..9857863933f 100644
--- a/dialogflow/analyze_content_stream_test.py
+++ b/dialogflow/analyze_content_stream_test.py
@@ -77,7 +77,6 @@ def participant_id(conversation_id):
 def test_analyze_content_audio_stream(capsys, conversation_id, participant_id):
     # Call StreamingAnalyzeContent to transcribe the audio.
     participant_management.analyze_content_audio_stream(
-        project_id=PROJECT_ID,
         conversation_id=conversation_id,
         participant_id=participant_id,
         audio_file_path=AUDIO_FILE_PATH,
diff --git a/dialogflow/participant_management.py b/dialogflow/participant_management.py
index e2bf6169f43..8df9e4e45de 100644
--- a/dialogflow/participant_management.py
+++ b/dialogflow/participant_management.py
@@ -16,6 +16,7 @@
 """Dialogflow API Python sample showing how to manage Participants.
 """
 
+import google.auth
 from google.cloud import dialogflow_v2beta1 as dialogflow
 
 ROLES = ["HUMAN_AGENT", "AUTOMATED_AGENT", "END_USER"]
@@ -112,12 +113,11 @@ def analyze_content_text(project_id, conversation_id, participant_id, text):
 
 # [START dialogflow_analyze_content_audio_stream]
 def analyze_content_audio_stream(
-    project_id, conversation_id, participant_id, audio_file_path
+    conversation_id, participant_id, audio_file_path
 ):
     """Analyze audio content for END_USER
 
     Args:
-        project_id: The GCP project linked with the conversation profile.
         conversation_id: Id of the conversation.
         participant_id: Id of the participant.
         audio_file_path: audio file in wav/mp3 format contains utterances of END_USER."""
@@ -127,7 +127,8 @@ def analyze_content_audio_stream(
     # After completing all of your requests, call the "__exit__()" method to safely
     # clean up any remaining background resources. Alternatively, use the client as
     # a context manager.
-    client = dialogflow.ParticipantsClient()
+    credentials, project_id = google.auth.default()
+    client = dialogflow.ParticipantsClient(credentials=credentials)
 
     participant_path = client.participant_path(
         project_id, conversation_id, participant_id