Active Noise Control Demo
With this shareware, you can test and experiment with a very simple active noise control system at home. The purpose of this experiment is to demonstrate active noise control. The basic principle of active noise control is to cancel a sound wave (noise) by emitting a secondary opposite (out-of-phase) sound wave (control wave). The active noise control principle is illustrated in the figure below. In the real world, the implementation of active noise control is much more complex due to phase and spatial matching, efficient transducers, system identification, etc., as explained in the paper "Active Control of Sound and Vibration," by C. R. Fuller and A. H. Flotow.
The shareware that you can download, sends a single frequency wave (sine wave at 1000 Hz) to your right speaker. This sound wave represents the noise to be cancelled. By activating the control (pushing on the control button in the program), sound wave of equal amplitude and opposite phase is sent to the left speaker to cancel the noise. Note that for an effective demonstration, the two speakers should face each other and be close to one another (see picture above). If desired, the speakers can then be moved apart and the resulting effect on the sound cancellation observed.
This share was tested using "Labtec LCS-800" speakers; the sound cancellation obtained was large and appreciable. Note that the control results depends highly on the quality of speakers used. Please make sure that the volume of each speaker is set to be identical. Also notice that this experiment is more impressive at medium-high volume (please be careful not to overdrive your speakers and ears!).
What you need to run the program:
- PC with Windows 3.1 (or higher).
- Stereo sound card configured to work under Windows Operating System.
- 2 speakers that can be positioned as desired (i.e., not attached to the computer screen or embedded in the PC).
To set-up the active noise control experiment:
- Download the program in a temporary directory.
- To get the executable file:
- Rename ANCware.zip to ANCware.exe.
- Double click on ANCware.ee. It will automatically unzip itself in your directory and four files will be created (one executable file"ANC_demo.exe" and three files ".dat").
- Unzip ANCware.zip using PKunzip (DOS or Windows) in your directory and four files will be created (one executable file"ANC_demo.exe" and three files ".dat").
- Double click on "ANC_demo.exe" to start the program.
- Follow the instructions displayed by the program.
WARNING: This shareware and the accompanying files are given "as is" and without warranties. The VAL assumes no liability for damages, direct or consequential, which may result from its use.
WARNING: This shareware and the test arrangement for the demonstration of active control is COPYRIGHT 1996, to Vibration and Acoustics Laboratories, Virginia Polytechnic Institute and State University (ALL RIGHTS RESERVED). The shareware can be used for personal purposes without restrictions, but cannot be used for commercial purposes without the permission of the Vibration and Acoustics Laboratories. For more information on use of this shareware for other than personal purposes, please contact the VAL Director.