Clarify pcm format

Author: rattrayalex

openapi.yaml

@@ -6930,7 +6930,11 @@ components:
           type: string
           enum: ["alloy", "echo", "fable", "onyx", "nova", "shimmer"]
         response_format:
-          description: "The format to audio in. Supported formats are `mp3`, `opus`, `aac`, `flac`, `pcm`, and `wav`."
+          description: |-
+            The format to return audio in. 
+            Supported formats are `mp3`, `opus`, `aac`, `flac`, `pcm`, and `wav`. 
+            
+            The `pcm` audio format, similar to `wav` but without a header, utilizes a 24kHz sample rate, mono channel, and 16-bit depth in signed little-endian format.
           default: "mp3"
           type: string
           enum: ["mp3", "opus", "aac", "flac", "pcm", "wav"]