Frequency Loom

v1.2 — June 2026

A professional audio measurement bench: spectrum, SPL, RT60 with multiband per-octave decay analysis, tuner, loudness, NC-curve overlay, PDF export, and room treatment advisor — all on-device, no account required.

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What's New in 1.2

Multiband RT60 NEW — after any impulse capture, see T20 reverberation time computed independently for 7 octave bands (63 Hz through 4 kHz). IIR biquad bandpass filtering + Schroeder backward integration per band — the same methodology as Room EQ Wizard. Tap any bar for its full Schroeder decay curve. Pass/fail comparison against EBU R 68 / ISO 3382-1 control-room targets.

What's New in 1.1

NC Curve Overlay — overlay any NC-15 through NC-65 reference curve on the real-time spectrum; live NC rating badge updates continuously
PDF Export — export an octave-band SPL report with chart and NC evaluation from the RTA screen
Room History — browse all saved RT60 measurements with trend chart, FFT snapshot, and swipe-to-delete
Room EQ Advisor — select a room type to get RT60 targets, NC goals, and ranked acoustic treatment recommendations

Core Tools

Real-time spectrum analyzer (1/1 to 1/24 octave, peak hold, NC overlay)
A / C / Z weighted SPL meter — Slow, Fast, Impulse, LEQ
Scrolling spectrogram with magma colormap
Chromatic tuner with YIN pitch detection and cents readout
LUFS loudness metering (ITU-R BS.1770 K-weighting)
RT60 + Multiband RT60 — wideband and per-octave-band Schroeder decay
Tone generator: sine, log sweep, pink / white / brown noise, impulse
Standing-wave heatmap across 12 positions
Audiogram hearing sweep, Crossover designer, Hum ID, Time Align, Vocal Warmup, OSHA Dosimeter (CSV export), Phantom 48V tester

Multiband RT60 — What Is It?

A single wideband RT60 number hides the most common problem in room acoustics: bass modes that ring far longer than the rest of the frequency range. A room measuring 0.5 s broadband could have a 63 Hz decay of 2 seconds — making bass-heavy mixes impossible to evaluate. Frequency Loom 1.2 adds per-octave-band analysis across 63, 125, 250, 500, 1000, 2000, and 4000 Hz.

Each band is processed with a second-order IIR biquad bandpass filter (Q = 1/√2, one-octave bandwidth) followed by Schroeder backward integration. The T20 slope (−5 to −25 dB segment) is extracted by linear regression; RT60 = T20 × 3. An R² confidence score is shown alongside each result. Results are compared against EBU R 68 / ISO 3382-1 control-room targets with per-band pass/fail indication.

NC Curve Overlay — What Is It?

The Noise Criterion (NC) system (ANSI/ASA S12.2-2019) defines the maximum permissible background noise level in each octave band for a given occupancy. A recording studio typically targets NC-15 to NC-20; a classroom NC-25 to NC-35; a restaurant NC-40 to NC-55. Frequency Loom overlays these standard curves directly on the live spectrum so you can see in real time whether your HVAC, equipment fan noise, or street noise is within spec.

The Room EQ Advisor cross-references your measured RT60 with AES, EBU, and ASHRAE guidance to suggest how much absorption, bass trapping, or diffusion to add — and which room positions to target first.

Fully Offline · No Account · No Tracking

Frequency Loom stores all measurements on your device using SwiftData. The only permission the app requests is the microphone. No data leaves your iPhone — no analytics SDK, no network requests, no ads.

Last updated June 17, 2026