Often abbreviated as RTA, a real time analyzer is a tool used in pro audio for evaluating the levels of different frequencies in an electronic signal (often generated by a microphone). An RTA usually confines itself to the frequencies between 20hz and 20khz (the range of human hearing). It's most common uses are for citing problem frequencies (excessively loud bad sounding ones) and for tuning a sound system for flat frequency response. An RTA is usually used in conjunction with a mic with flat frequency response.