A self-contained motion sensitive audio module includes a sensor circuit coupled to a pyroelectric infrared sensor with two sensing elements configured for reliably sensing passersby. The module also includes a power supply, a timing circuit, an audio circuit, a speaker and optionally an LED. The sensor circuit produces an amplified trigger signal when a passerby is sensed. The sensor circuit includes an amplifier to amplify the trigger signal. The timing circuit produces an activation signal upon receiving a trigger signal from the sensor circuit. In playback mode, the audio circuit produces an audible sign message output upon receiving an activation signal from the timing circuit. The module may be attached to the back side of a sign with apertures for receiving the sensor, speaker and optionally an LED.