# lidcreak — the lid-creaking sound FreeSlapMac forgot to implement FreeSlapMac (the free version of SlapMac) ships a **"Lid Creaking Sound"** switch that does nothing. It isn't a permissions problem and it isn't your Mac: the free app's binary contains the toggle, the description and the `_creakingEnabled` preference — and **no lid-sensor code at all**, no `creaking.mp3` reference, and no wake/clamshell hooks. The switch is dead UI carried over from the paid app, which does have a `LidAngleSensor` / `CreakAudioEngine` implementation. The `creaking.mp3` asset is sitting right there in the bundle, unused. This is a ~380-line user-level helper that reads the MacBook's hidden lid-angle sensor and plays that unused asset while the lid moves. The app's own switch becomes the on/off control. ``` lidcreak/ ├── lidcreak.py the daemon (IOHID feature-report read + afplay) ├── install.sh copies it, writes the LaunchAgent, self-tests it ├── uninstall.sh removes every trace ├── README.md └── LICENSE ``` ## Requirements | | | |---|---| | Mac | Apple Silicon MacBook (the lid-angle sensor is exposed on macOS 13+; verified on Mac14,2 / M2 Air, macOS 26.6) | | App | FreeSlapMac installed in `/Applications` (or `~/Applications`) — provides `creaking.mp3` | | Python | any `python3` (the one from Command Line Tools is enough) | | Root | **none** — feature-report HID reads are unprivileged | ## Install ```bash unzip freeslapmac-lidcreak-1.0.1.zip cd freeslapmac-lidcreak bash install.sh ``` It prints a step-by-step report and ends with a self-test that reads your real lid angle and plays one creak. Nothing to approve, no login items to click, no System Settings trip. If the self-test says `SYSTEM OUTPUT: volume=0 muted=True`, nothing on your Mac can be heard — not this helper, not music, not anything. Unmute first: ```bash osascript -e 'set volume output muted false' -e 'set volume output volume 60' python3 "$HOME/Library/Application Support/FreeSlapLidCreak/lidcreak.py" --prove ``` `--prove` plays the creak three times at rising gain so you can hear exactly what you are choosing between. ## Verify ```bash tail -f ~/Library/Logs/lidcreak.log # tilt the screen: move … CREAK / skip:slow python3 "$HOME/Library/Application Support/FreeSlapLidCreak/lidcreak.py" --self-test launchctl list | grep lidcreak # agent is loaded and alive ``` A real session looks like this — 20 Hz sampling, one creak per movement burst: ``` 20:31:03 move 80->85 deg speed=32.9 deg/s CREAK 20:31:03 creak vol=1.82 20:31:03 move 84->80 deg speed=39.6 deg/s skip:retrigger (one creak per movement) 20:31:13 move 95->94 deg speed=4.6 deg/s skip:slow (drift, ignored) ``` ## Uninstall ```bash bash uninstall.sh # from the extracted folder ``` Removes the agent, the helper, and the logs. FreeSlapMac is not touched. ## How it works The MacBook's lid angle is a HID sensor on **usage page `0x20`, usage `0x8A`**, read as **feature report 1** (3 bytes: report ID, then the angle as uint16 little-endian — `01 68 00` = 104°). `lidcreak.py` polls it at 20 Hz through `IOHIDManagerCreate` + `IOHIDDeviceGetReport`, computes `Δangle / Δt`, and: - fires when speed ≥ **8 °/s** (so slow drift and typing vibration stay silent), - holds a **1.4 s** retrigger gap so one lid movement gives one creak, - sets gain from speed: `clamp(1.0 + speed/40, 1.0, 2.0)` — `creaking.mp3` is mastered about 30 dB below the tap sounds (mean −30.5 dBFS, peak −6.2 dBFS), so a "reasonable" 0.35 volume was inaudible even at full system volume. 2.0 is the loudest setting that does not clip, - plays with `afplay -t 1.8` (truncated to the creak, not the whole 5.1 s file), - reopens the device if the lid closes (the sensor disappears on sleep) instead of dying, - obeys `_creakingEnabled` and nothing else: it creaks with FreeSlapMac open or quit, because the app was never the thing playing this sound (1.0.0 required the app to be running, which meant a closed app produced silence and no explanation), - logs *why* a movement did not creak (`skip:slow`, `skip:toggle off`, `skip:retrigger`), and warns once when the system output is muted or at zero. Tuning knobs (no reinstall needed, edit the `ProgramArguments`/constants or pass flags): ```bash lidcreak.py --watch # live angle + speed, to pick your own threshold lidcreak.py --trigger 5 # more sensitive lidcreak.py --volume 1.5 # fixed gain (1.0-2.0) instead of speed-scaled lidcreak.py --prove # three creaks, quiet to loud lidcreak.py --trigger-test # offline check of the trigger logic, no audio ``` ## Honest limitations - **Closing the lid will not creak.** macOS suspends the machine as the lid reaches ~10°, so the sensor is gone before the hinge gets there. The creak fires while the lid *moves* — the same behaviour the paid app has. This is physics, not a bug in the helper. - **It is not a patch of the app.** The toggle in FreeSlapMac is still dead UI; this helper just reads it. Uninstalling the helper (or turning the toggle off) restores silence. - **Audio goes through `afplay`**, i.e. routes wherever system output goes. There is no mixing into the app's own audio session — the app never had one for this. - The sensor exists on Apple Silicon MacBooks; on Intel Macs and desktops `install.sh` says so and leaves nothing running. - FreeSlapMac's slap detection itself is untouched. One quirk worth knowing: if several copies of the app's privileged wrapper are alive, a single slap can retrigger more than once. Quitting and reopening the app collapses them to one. ## License MIT — see `LICENSE`. The `creaking.mp3` asset is **not** redistributed here: it is read from your own FreeSlapMac installation. FreeSlapMac and SlapMac are the work of their respective authors; this helper is an independent, unofficial companion. Written by Isaac Chan, October 2026. ## Changelog **1.0.1** — the version that actually makes a noise. Three faults, all found by reading the log instead of trusting the code: 1. The daemon only played while FreeSlapMac was open. The app was never the thing playing the creak, so that gate only ever produced silence with the app quit — and the log said `trigger=no`, which reads like "your lid didn't move enough". 2. Gain. `0.35` on a file mastered at −30.5 dBFS mean is inaudible even at full system volume. Now `1.0–2.0`, measured against the file's −6.2 dBFS peak so it cannot clip. 3. No audio diagnostics. A muted Mac and a missing creak looked identical. `--self-test` now prints the output volume and mute state, the daemon warns once if the output is muted, and each skipped movement is tagged with its reason. **1.0.0** — first release: HID sensor read, speed trigger, retrigger gap, LaunchAgent, self-test.