Based on a commercially available audio speaker a real- time rapid scanning interferometric SHG autocorreiator that may monitor both the pulse-width and frequency sweep in ultrashort laser pulses is reported. The repetition rate of sweeping is 1-20 Hz, and the measurement error is below 3 fs. This apparatus can be used widely for monitoring and measuring interferometric autocorrelation traces of femtosecond pulses generated from self-mode-locked Ti:sapphire laser and those from any other kind of femtosecond pulse lasers.