Merge pull request #222514 from sally-baolian/patch-86

Update record-custom-voice-samples.md

Author: prmerger-automator[bot]

articles/cognitive-services/Speech-Service/record-custom-voice-samples.md

@@ -20,7 +20,17 @@ Creating a high-quality production custom neural voice from scratch isn't a casu
 
 Before you can make these recordings, though, you need a script: the words that will be spoken by your voice talent to create the audio samples.
 
-Many small but important details go into creating a professional voice recording. This guide is a roadmap for a process that will help you get good, consistent results.
+Many small but important details go into creating a professional voice recording. This guide is a roadmap for a process that will help you get good, consistent results. 
+
+## Tips for preparing data for a high-quality voice
+
+A highly-natural custom neural voice depends on several factors, like the quality and size of your training data. 
+
+The quality of your training data is a primary factor. For example, in the same training set, consistent volume, speaking rate, speaking pitch, and speaking style are essential to create a high-quality custom neural voice. You should also avoid background noise in the recording and make sure the script and recording match. To ensure the quality of your data, you need to follow [script selection criteria](#script-selection-criteria) and [recording requirements](#recording-your-script). 
+
+Regarding the size of the training data, in most cases you can build a reasonable custom neural voice with 500 utterances. According to our tests, adding more training data in most languages does not necessarily improve naturalness of the voice itself (tested using the MOS score), however, with more training data that covers more word instances, you have higher possibility to reduce the DSAT (dis-satisfied part of the speech, for example, the glitches) ratio for the voice. 
+
+In some cases, you may want a voice persona with unique characteristics. For example, a cartoon persona needs a voice with a special speaking style, or a voice that is very dynamic in intonation. For such cases, we recommend that you prepare at least 1000 (preferably 2000) utterances, and record them at a professional recording studio. To learn more about how to improve the quality of your voice model, see [characteristics and limitations for using Custom Neural Voice](/legal/cognitive-services/speech-service/custom-neural-voice/characteristics-and-limitations-custom-neural-voice?context=/azure/cognitive-services/speech-service/context/context).
 
 ## Voice recording roles