Privacy Policy

Check1.2 - Feedback Checker

This is the privacy policy of the iPhone app "Check1.2 - Feedback Checker" ("this app").

This app does not collect any information that can identify you, such as your name or email address. Recordings, videos, measurement results and quiz scores are stored on your iPhone. Your Daily Ear Training score is sent to Apple's Game Center only while you are signed in to Game Center (see "About the Daily Ear Training (Game Center)" below). Information reaches the developer only in the cases described under "What reaches the developer" below.

Where it is stored

• Recorded audio, recorded video, analysis results and your voice reference are all stored on your iPhone. This app never sends them anywhere.
• Monitor check results, and any venue name or note you write on them, are also stored on your iPhone alone. They are never sent anywhere.
• Recordings, video and analysis are never sent to any server. The only network use this app starts itself is Apple's in-app purchase processing, and the Daily Ear Training's exchange with Game Center (Apple): sending your score and reading that day's rank and number of players. How in-app purchases and Game Center handle data is covered by Apple's Privacy Policy. When you tap a link such as Support, the page opens in your browser, such as Safari.
• No advertising, no tracking, no analytics tools are used.

What reaches the developer

• Contact email: if you send an email from Contact, the developer receives your email address and message. It is used only to reply and to fix the app, and is never passed to anyone else.
• Totals from Apple: if Share With App Developers is on in the iPhone's Settings > Privacy & Security > Analytics & Improvements, Apple shares crash logs and usage statistics for this app with the developer. Apple collects this data anonymously (Apple's explanation). If it is off, nothing is shared.
• Download and purchase counts on the App Store reach the developer only as totals counted by Apple. The developer cannot tell who bought the app.
• Daily Ear Training ranking: the developer can also see the top 100 scores and players through Apple's App Store Connect (Apple's explanation). This is used only to remove fraudulent scores.

About sharing results

• Tapping "Share result" in the quiz or the Daily Ear Training opens the iPhone's standard share sheet.
• What it sends is only your score and rank (the number of correct answers in the Daily Ear Training) and a link to the App Store.
• Whether to send it, and to whom, is your choice. Nothing reaches the developer.

About iPhone backup

If iCloud Backup is on for your iPhone, this app's recordings and videos are included in the iPhone's overall backup, just like data from Photos, Notes and other apps. That backup goes to your own iCloud - it is not sent to the developer, and the developer cannot see inside it. To keep a recording or video out of the backup, delete it from Recordings.

About in-app purchases

The Full version purchase is handled by Apple through the App Store. The developer never receives your name, card details or anything similar.

Changes to this app

The features of this app, and what the free version covers, may change without notice. No recording or monitor check result already stored on your device is removed by such a change.

About microphone use

This app uses the microphone to check the sound of a PA or stage monitor. On screens that record, the screen shows that recording is in progress (and the iPhone itself shows an indicator at the top while the microphone is in use). Recorded audio is stored on the device only, and is used inside the app for analysis, playback and the sound of your videos. This app never sends it anywhere.

You can turn microphone access off at any time in the iPhone's Settings > Check1.2 > Microphone. Turning it off stops the features that record; everything else still works.

About camera use

This app uses the camera only when you choose Video in Stereo recording, to combine the camera picture and the stereo recording's sound into one video. While you record video, the iPhone itself shows an indicator at the top of the screen. The camera picture and the video are stored on your iPhone alone, and this app never sends them anywhere.

You can turn camera access off at any time in the iPhone's Settings > Check1.2 > Camera. Turning it off stops Video; everything else, including audio recording, still works.

About the Daily Ear Training (Game Center)

• Only while you are signed in to Game Center, the Daily Ear Training sends your score (and the total time you took to answer the 10 questions) to Apple's Game Center and reads that day's rank and number of players. Without signing in you can still use every feature except the ranking. Your record stays on your iPhone.
• A score you send appears in the ranking for other users, together with your Game Center nickname and avatar. Apple displays and stores it, and how it is handled is covered by Apple's explanation of Game Center and privacy.
• This app does not read, store or send your Game Center player name or ID.
• For an account that Game Center treats as underage, no score is sent and no ranking is shown.
• If you do not want to send your score, sign out in the Game Center item in the iPhone Settings app.

About notifications

A "Notify me when it resets tomorrow" button appears only when someone on the free version has used up today's 2 sets. Permission is requested only if you tap it, and one notification is sent the next morning. If you do not tap it, this notification is not sent. You can turn permission off at any time in Settings > Check1.2 > Notifications.

If you start the 7-day trial, the app asks for notification permission right after you start it. Only if you allow it, one notification is sent 2 days before the trial ends. It says only that the trial is ending, that you will not be charged automatically, that the free features stay available, and the one-time price of the Full version. You can turn this notification off with the switch on the Full version screen, or in iPhone Settings > Check1.2 > Notifications.

Deleting data

You can delete your voice reference at any time from "Delete voice reference" inside Recordings on the home screen.

Recordings and videos can be deleted at any time from Recordings on the home screen, one at a time or together (deleting them does not affect checks or your voice registration). Recordings and videos build up until you delete them (a monitor check or voice registration is about 4-6 MB each; stereo recording is about 1.9-23 MB per minute; a video is about 60 MB per minute). Deleting the app removes all of its data from the device.

Monitor check results can be deleted one at a time: open "Past results" on the Monitor check screen and swipe a row to the left (swipe right to pin it).

Recordings, and the file that logs your quiz scores (練習記録.csv), also appear in the iPhone's Files app (On My iPhone > Check1.2). You can take them out or delete them from there. All of it lives on this iPhone alone and is never sent anywhere.

Your Daily Ear Training record (correct answers and streak) also lives on this iPhone alone, and is removed when you delete the app. A score already sent to Apple's Game Center stays in Game Center, and this app cannot delete it.

About the numbers shown

Frequencies are shown in Hz and are found by parabolic interpolation (checked during development against known tones from 100 Hz up to 8000 Hz, with an error of about ±0.2 Hz). Feedback is detected by finding a single sustained tone that sticks out from its surroundings and telling it apart from a harmonic. That method follows work established in the AES, the audio engineering society (PNPR, PHPR, IPMP and others). Because feedback grows quickly in level, a sound that keeps rising is flagged early, in about a second. A sound that holds a steady level is checked for a few seconds first, to tell it from notes being played. The absolute level (dB) is not calibrated, so this is not a sound level meter, but that does not affect the frequency judgment, which is made from the difference against the surrounding bands.

What is not guaranteed

This app is not a measuring instrument. The numbers it shows are a guide for comparing sound in one place. It does not guarantee the accuracy of a calibrated instrument, compliance with regulations, or any judgment about acoustic safety. Always give priority to a proper external instrument and to the standards of the venue.

• Below 150 Hz the built-in iPhone microphone cannot measure accurately, so feedback is not judged there (it is still drawn on the analyzer and spectrogram screens).
• Absolute level in dB is not calibrated, so this app cannot be used as a sound level meter.
• The developer is not responsible for decisions or actions taken based on what this app shows.

About the app's introduction page (website)

Everything above is about the app itself. The app's introduction page, check12.da-win.net, uses Google Analytics to count how many people visit it. What it counts is when a page was viewed, which page it was, where the visitor came from, and whether a phone or a computer was used, in a form that does not identify the person. It does not collect names, email addresses or phone numbers.

For how Google handles this data, see Google's policies and terms. If you refuse cookies in your browser settings, you are not included in this count.

The app itself uses no analytics tools at all. Recording and analysis both happen only on your iPhone.

Contact

Support

How to use the app and answers to frequently asked questions are on the Support page.

Established: July 16, 2026 / Last updated: November 3, 2026