diff --git a/dspy/adapters/types/audio.py b/dspy/adapters/types/audio.py
index f39d60bda7..0ceb734b73 100644
--- a/dspy/adapters/types/audio.py
+++ b/dspy/adapters/types/audio.py
@@ -17,6 +17,11 @@
     SF_AVAILABLE = False
 
 
+def _normalize_audio_format(audio_format: str) -> str:
+    """Removes 'x-' prefixes from audio format strings."""
+    return audio_format.removeprefix("x-")
+
+
 class Audio(Type):
     data: str
     audio_format: str
@@ -61,6 +66,9 @@ def from_url(cls, url: str) -> "Audio":
         if not mime_type.startswith("audio/"):
             raise ValueError(f"Unsupported MIME type for audio: {mime_type}")
         audio_format = mime_type.split("/")[1]
+
+        audio_format = _normalize_audio_format(audio_format)
+
         encoded_data = base64.b64encode(response.content).decode("utf-8")
         return cls(data=encoded_data, audio_format=audio_format)
 
@@ -80,6 +88,9 @@ def from_file(cls, file_path: str) -> "Audio":
             file_data = file.read()
 
         audio_format = mime_type.split("/")[1]
+
+        audio_format = _normalize_audio_format(audio_format)
+
         encoded_data = base64.b64encode(file_data).decode("utf-8")
         return cls(data=encoded_data, audio_format=audio_format)
 
@@ -126,6 +137,9 @@ def encode_audio(audio: Union[str, bytes, dict, "Audio", Any], sampling_rate: in
             header, b64data = audio.split(",", 1)
             mime = header.split(";")[0].split(":")[1]
             audio_format = mime.split("/")[1]
+
+            audio_format = _normalize_audio_format(audio_format)
+
             return {"data": b64data, "audio_format": audio_format}
         except Exception as e:
             raise ValueError(f"Malformed audio data URI: {e}")
diff --git a/tests/adapters/test_audio.py b/tests/adapters/test_audio.py
new file mode 100644
index 0000000000..b7597fbd29
--- /dev/null
+++ b/tests/adapters/test_audio.py
@@ -0,0 +1,32 @@
+import pytest
+
+from dspy.adapters.types.audio import _normalize_audio_format
+
+
+@pytest.mark.parametrize(
+    "input_format, expected_format",
+    [
+        # Case 1: Standard format (no change)
+        ("wav", "wav"),
+        ("mp3", "mp3"),
+
+        # Case 2: The 'x-' prefix
+        ("x-wav", "wav"),
+        ("x-mp3", "mp3"),
+        ("x-flac", "flac"),
+
+        # Case 3: The edge case
+        ("my-x-format", "my-x-format"),
+        ("x-my-format", "my-format"),
+
+        # Case 4: Empty string and edge cases
+        ("", ""),
+        ("x-", ""),
+    ],
+)
+def test_normalize_audio_format(input_format, expected_format):
+    """
+    Tests that the _normalize_audio_format helper correctly removes 'x-' prefixes.
+    This single test covers the logic for from_url, from_file, and encode_audio.
+    """
+    assert _normalize_audio_format(input_format) == expected_format