Tap the microphone prompt to grant access, then choose any tool from the tab bar or the "More Tools" screen. The SPL Meter and Spectrum Analyzer start streaming immediately. For RT60 and Multiband RT60, use the Tone Generator's impulse signal or a hand clap, then capture the decay.
Support — v1.2
Frequency Loom Support
Help, troubleshooting, and contact information for Frequency Loom v1.2.
Microphone access is the only permission Frequency Loom requests. It is used exclusively for audio measurement: spectrum analysis, SPL, RT60 capture, tuning, and loudness metering. No audio is recorded or transmitted.
Email via the App Store product page with your iPhone model, iOS version, and a short description of what happened. Include which tool you were using (e.g. "Multiband RT60 on iPhone 15 Pro, iOS 17.5").
Frequently Asked Questions
How do I use Multiband RT60?
First measure an impulse response in the RT60 screen (balloon pop, hand clap, or the app's built-in impulse tone). After the decay is captured and the wideband RT60 result appears, a "View Multiband RT60" button appears below the decay chart. Tap it to see independent T20 values for 63 Hz through 4 kHz, plotted as a bar chart with EBU R 68 / ISO 3382-1 control-room target lines. Tap any bar to see its full Schroeder decay curve.
What is T20 / Schroeder backward integration?
T20 measures the time for the impulse response energy to decay by 20 dB (from −5 to −25 dB below peak). That slope is multiplied by 3 to give the RT60 estimate. Schroeder backward integration accumulates the squared impulse response from the noise floor backward to the peak, producing a smooth decay curve that is more robust to background noise than a direct energy measurement.
What are the EBU R 68 / ISO 3382-1 target lines?
EBU R 68 (European Broadcasting Union) and ISO 3382-1 specify target reverberation times for control rooms and listening environments. Lower frequencies (63–250 Hz) are allowed slightly longer decay than mids and highs. Frequency Loom compares each band's measured T20 against these published targets and shows a pass or fail indicator.
The Multiband RT60 button does not appear — why?
The button is only shown after a successful impulse response capture that produces a non-empty sample buffer. Make sure the impulse or clap is loud enough that the wideband RT60 value appears first. The room must be quiet during the decay (typically 2–4 seconds of quiet after the impulse).
What do the NC curve overlay numbers mean?
The Noise Criterion (NC) rating represents the maximum allowed background noise level at a given octave band. For example, NC-25 means background noise in each band must stay below the NC-25 reference curve (ANSI/ASA S12.2-2019). The live badge shows the effective NC rating of the current noise floor.
How accurate is the SPL reading?
iPhone microphones are not calibrated SPL meters. The reading is an approximation valid to roughly ±3 dB in the 500 Hz – 8 kHz range without calibration. Use the Settings calibration offset to align to a known reference (pistonphone at 94 dB / 1 kHz is ideal).
Does the app require an account?
No. Frequency Loom requires no account, login, or network connection. All data stays on your device.
Where is my data stored?
Measurements, audiograms, dosimeter sessions, and warmup sessions are stored in SwiftData databases on your device. They are included in your device's encrypted backup and iCloud backup if enabled. Nothing is sent to a server.
How do I delete all my data?
Delete the app. iOS removes its SwiftData containers when the app is uninstalled.
Frequency Loom v1.2 · Updated June 17, 2026