pipe up - Phrases/Idioms
The American Heritage® Dictionary of Idioms by Christine Ammer. Copyright © 2003, 1997 by The Christine Ammer 1992 Trust. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Speak up, as in Finally she piped up, “I think I've got the winning ticket,” or Pipe up if you want more pancakes. This term originally referred to a high, piping tone. [Mid-1800s]