The PNG-2000 is designed as a portable acoustic noise-generating unit that can be used in a variety of ways. The noise generating circuitry has been optimized for voiceband noise masking against listening devices and is designed to reduce the effectiveness of eavesdropping devices such as microphones and tape recorders. When multiple units are used in concert, a complete environment masking system can be easily installed in any environment. The PNG-200 can be mounted to smooth surfaces using suctions cups or simply placed in an area that potential eavesdropping devices may be present.