In Word 2007, click the Office button and then click Word Options. Then, select Reviewing and select Insert Voice.

If the Insert Voice icon isn’t visible, add it: Click the Reviewing toolbar’s drop-down arrow (at the right end) and choose Add Or Remove Buttons.

Display the Reviewing toolbar: From the View menu, choose Toolbars and then select Reviewing or right-click the background of any toolbar and select Reviewing.

Hardware issues aside, inserting a voice comment is easy: It won’t help to insert a voice comment the recipient can’t hear. If you can’t control the recipient’s hardware, you might want to skip this option. The creator needs a microphone and the recipient needs speakers. Of course, this feature is dependent upon the creator and the recipient having the appropriate hardware, so it won’t work for everyone.

When something doesn’t lend itself well to the written language, you can insert a voice comment. For instance, you might want to include a personal greeting or clarify a point. We use Word to share information and ideas via the written word, but there’s more to Word than that. When written words just won't do, provide a personal touch by inserting a voice comment into a Word document. Insert voice comments into a Word document

How to insert comments in word 2010