Or by full definition, a single frequency audio spectrum volume meter. This is made possibly in a simple way, using an Arduino, eight bright LEDs and an audio socket wired into the analogue input. The Beat Sync can isolate a certain frequency, and display the level using the eight LEDs. For example:
When making projects that require various LED effects and simple LEDs just aren't enough - consider using a Freetronics Dot Matrix Display:
Available in a variety of colours, they consist of a 32 by 16 matrix of LEDs. Included with the DMD is a cable to directly connect with an Arduino-compatible board, and at low brightness (which is still fine to read indoors) you can power one DMD from the Arduino. However by connecting 5V at 2.5A for each board they operate at a brightness which is visible anywhere. Furthermore you can daisy-chain (with the included cable) six or more displays for great effects. So for more information head over to the DMD pages today.