A microphone is required, and your browser must have permission to access it. If no microphone is connected ,your microphone is disabled, or the input volume is insufficient, a warning icon will appear in the bottom right of the display.
April 2019 Update -- Added rudimentary code to detect when the browser cannot access or detect a microphone. July 2017 Update -- Added a visual maximum value indicator. Toggle on/off with the space-bar. (Update: Off by default + smaller pointer) May 2017 Update II - Re-implemented the scrolling-line graph in a much better way. May 2017 Update -- Added a scrolling-line graph that shows the past few seconds of data. Volume (Noise!) sensor implemented as an analogue display with an exponential moving average providing the displayed value. This smooths the output and makes the meter respond only to constant background noise. Created to demonstrate to my students that Scratch can be used to create more than games and simple animations! I actually use this in class!