# Soundmark: Sound Collection — Field recorder & spectrogram

> Field recorder & spectrogram (iPhone/iPad app by 鹏帆 张.)

- Source: https://appshunter.io/ios/app/soundmark-sound-collection/id6792312467 (this page in markdown: same URL + `.md`)
- Developer: [鹏帆 张](https://appshunter.io/developer/6774531925)
- Category: Lifestyle
- Price: $0.99
- Age rating: 4+
- Requires: iOS 17.0 · 25 MB
- Languages: Japanese, French (France), Chinese (Simplified, China), American English, European Spanish
- Released: 2026-07-29
- Data updated: 2026-08-13
- User reviews in markdown: https://appshunter.io/ios/app/soundmark-sound-collection/id6792312467/reviews.md

## What is Soundmark?

A nocturnal field-recording notebook.

Record whatever you can hear right now — rain on a balcony awning, the wind a train pushes out of a tunnel, a convenience-store freezer at two in the morning. Trim the ends off, give it a title and a place, attach a photo if the moment needs one. Then let your iPhone take it apart.

ANALYSED ON THE DEVICE
Every recording is analysed in full the moment you save it: FFT and short-time Fourier transform, on the phone. You get the waveform, the spectrum, a spectrogram, and a Fourier-series view that draws the five strongest components as sine curves — alongside dominant frequency, loudness in RMS dB, spectral centroid, zero-crossing rate and sample rate. No queue, no upload; it finishes just the same in airplane mode.

THREE STEPS INTO THE LIBRARY
• Record — 48 kHz, with the live waveform and the dominant frequency moving with whatever is in front of you. Choose the back, front or bottom microphone; for ambience, the one facing the world is usually the right one.
• Trim — drag the two handles until only the part worth keeping is left. Trimming writes a new file and re-runs the analysis.
• Note — add a title, a place and a description, and attach photos or a video if the moment needs them.

EVERY SOUND GETS ITS OWN COLOUR
The dominant frequency, 60 Hz to 4 kHz, is taken on a log scale and mapped onto hues from amber to violet. The low hum of a freezer runs warm; the fine hiss of a mountain stream runs cold. The colour isn't decoration — it's a reading, and it follows the audio when you re-trim it.

WHILE IT PLAYS
Scrub the waveform with your finger and the spectrum follows the playhead, reading the real STFT column underneath it rather than a decorative shimmer.

NOTHING LEAVES THE PHONE
No accounts, no servers, no analytics, no third-party SDKs, and not a single network request anywhere in the code. Recordings, attachments and the index are written into the app's own Documents directory and synced nowhere. The place is a line of text you type — the app never reads your location. Photos and video arrive through the iOS picker, so Soundmark never gets access to your photo library. Delete a recording and its audio and attachments go with it; delete the app and everything is gone.

FREE
No in-app purchases, no subscription, no ads.

iOS 17 or later. iPhone. Dark by design — it was made for the hours when the world is quiet enough to hear.


## Version history (last 1 release)

### 1.0 — 2026-07-29

No release notes.

## More apps by 鹏帆 张

- [Linger: NFC Photo & Video](https://appshunter.io/ios/app/linger-nfc-photo-and-video/id6775706704)
- [Smashphone: Pickleball, Tennis](https://appshunter.io/ios/app/smashphone-pickleball-tennis/id6779093089)

All apps by 鹏帆 张: https://appshunter.io/developer/6774531925

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*Data collected daily from the US App Store and indexed by [AppsHunter](https://appshunter.io/). User reviews are verbatim App Store reviews. Ratings, prices and chart positions refresh continuously; this snapshot is from 2026-08-13.*