Real-Time Analyzer (RTA)
Definition
Real-Time Analyzer (RTA)
A Real-Time Analyzer (RTA) is a measurement instrument that displays the frequency spectrum of a live audio signal, typically in 1/1 or 1/3 octave bands, with continuous updates. RTAs apply FFT analysis and band-energy summation to show amplitude versus frequency. SonaVyx provides a full-featured RTA directly in your browser using Rust WASM processing.
Band level = 10 × log₁₀(Σ |X[k]|² for bins in band) dB, where X[k] = FFT bin magnitude
How RTA Is Measured
An RTA captures audio through a microphone, performs FFT analysis, groups the resulting frequency bins into octave or fractional-octave bands, and displays the energy in each band as a bar chart. SonaVyx updates the display at 20 to 60 frames per second using overlapped FFT processing. Band widths follow IEC 61260-1 center frequencies for standardized 1/1 and 1/3 octave analysis.
Practical Example
A sound engineer plays pink noise through a PA system and views the RTA display on SonaVyx. The 1/3 octave bars show a +6 dB peak at 125 Hz and a -4 dB valley at 4 kHz relative to the flat reference. The engineer applies parametric EQ to flatten the response, watching the RTA bars converge toward the target line in real time.
RTA vs FFT Display
A narrow-band FFT display shows individual frequency bins with resolution determined by FFT size (e.g., 11.7 Hz per bin at 4096 points / 48 kHz). An RTA groups these bins into standardized octave or fractional-octave bands, smoothing the display and making it easier to identify broad trends. RTA is preferred for live system tuning because the band-averaged view is more stable and easier to interpret quickly during a performance.
Octave Band Standards
IEC 61260-1:2014 defines the center frequencies and bandwidth for octave and fractional-octave filters. The 1/1 octave centers are 31.5, 63, 125, 250, 500, 1000, 2000, 4000, 8000, and 16000 Hz. Each 1/3 octave band has a bandwidth factor of 2^(1/3) ≈ 1.26, providing three bands per octave. SonaVyx supports both 1/1 and 1/3 octave RTA modes with energy-correct band summation from the underlying FFT data.
Pink Noise Calibration
Because pink noise has equal energy per octave, it appears as a flat line on a correctly calibrated RTA display. If the RTA shows a slope or bumps when measuring pink noise through a known-flat system, the microphone calibration may be inaccurate. SonaVyx supports loading calibration files (.cal, .frd) that compensate for microphone frequency response, ensuring accurate RTA readings.
RTA in Live Sound
During live events, RTA provides instant visual feedback on the spectral balance of the mixed program material. Engineers monitor the RTA to ensure bass levels are controlled, midrange clarity is maintained, and high frequencies are not excessively bright or dull. A-weighted or C-weighted RTA views help assess compliance with venue SPL limits in real time.
Try It Now
Open Real-Time Analyzer — free in your browser