Hello Rodney, Thanks for the message. The calibrator is designed to operate solely at 1kHz and either of two or three levels. This means we can make it very stable. It is also corrected for atmospheric conditions. The sound meter is far more likely to change with time and environmental parameters. This means we can generally rely more on the calibrator than the sound meter. Furthermore, international standard dictate that even if your sound meter is not verified each year by a calibration laboratory, your calibrator must. You can calibrate on ‘A’, ‘C’, or ‘Z’ weighting as all of these filters are set to be zero at 1kHz. We hope this helps. The Castle Team

Hi CJ, you can see our new Calibrator here: www.castleshop.co.uk/dbcal-triple-level-acoustic-calibrator.html this retails at £285.00. Many thanks.