12‑TET pitch mapping from ~20 Hz to 20 kHz with note names, exact Hz, and MIDI note numbers.
Useful for tuning, labeling FFT peaks, and quick pitch↔frequency reference.
Note
MIDI
Frequency (Hz)
1/3‑Octave Bands (centers + edges)
1/3‑octave filter-bank banding (centers + ±1/6‑oct edges) across ~20 Hz–20 kHz.
Useful for RTA/measurement displays, acoustics reporting, and broad‑stroke EQ.
Band #
Center (Hz)
Lower (Hz)
Upper (Hz)
Edges: ±1/6 octave around center.
ISO 226 Equal‑Loudness Contours (0–90 phon)
ISO 226 equal‑loudness contours: SPL vs frequency needed for tones to be perceived as equally loud at a given phon.
Useful for loudness perception intuition and calibration context.
Note: ISO reference frequencies end at 12.5 kHz.
ISO coefficient reference (f, α, Lu, Tf)
f (Hz)
α
Lu (dB)
Tf (dB)
SPL at ISO reference frequencies (for shown phons)
Bark Bands (critical‑band edges + widths)
Bark critical bands (edges, centers, widths) derived from a Zwicker‑style Bark mapping.
Useful for masking/intelligibility reasoning and perceptual audio model intuition.
Band
z‑range
Low (Hz)
Center (Hz)
High (Hz)
Width (Hz)
z(f)=13·atan(0.00076·f)+3.5·atan((f/7500)^2)
ERB‑rate and ERB bandwidth (Glasberg & Moore)
ERB‑rate is a psychoacoustic frequency scale; ERB bandwidth approximates auditory filter width in Hz.
Useful for perceptual filterbank design, hearing/speech research, and “how wide is the ear’s filter here?” intuition.
Hz
ERB‑rate
ERB width (Hz)
Mel Scale
Mel is a perceptual pitch scale that compresses high frequencies.
Commonly used for mel filterbanks and MFCC pipelines in speech/audio ML.
Hz
Mel
mel = 2595·log10(1 + f/700)
Microtonal Scale (24‑TET, quarter‑tones)
24‑TET pitch grid referenced to A4=440 with step index and cents deviation at the cursor.
Useful for microtonal composition/tuning and quantization sanity checks.