Otolock

Sound Lock → OtoLock に変更しました。
OtoLock
"I let my kid watch videos, and before I knew it, the volume had crept way up."
"I just want to keep the volume fixed while I hand over my phone."
"I want to disable the volume buttons so my kid can't touch them."
That's exactly what OtoLock is for.
OtoLock is a simple app that temporarily locks your device's physical volume +/− buttons — perfect for those moments when you hand your phone or tablet to your child.
Whether you want to keep the volume right where it is, or make sure the volume buttons simply don't respond when pressed, OtoLock is there when you need it.
When you're done, just unlock it with a 4-digit PIN. No complicated setup every time.
Great for moments like:
Keeping the volume fixed while your kid watches videos
Temporarily disabling the volume buttons
Preventing accidental presses on the volume +/− buttons
Handing your phone or tablet over to your child
Letting kids use learning apps or games
Making sure no one bumps the volume up or down without you knowing
Whenever you just want the volume to stay put, OtoLock is ready in seconds.
How it works:
First, turn on OtoLock in Android's Accessibility settings.
Enter a 4-digit PIN to use for locking.
Tap "Lock Volume Buttons."
While locked, pressing the physical volume +/− buttons won't change the volume.
To unlock, enter the PIN you set.
You choose a new PIN each time you lock, so you can pick whatever you like for that session.
Lock it only when you need to
When OtoLock isn't active, the volume +/− buttons work exactly as usual.
Rather than restricting volume all the time, you can disable the buttons only when it matters — like while your device is in your child's hands — and turn it back on whenever you like. Also note that the lock automatically releases if the device restarts.
A focused feature, built to do one thing well
OtoLock only restricts one thing: volume changes made via the physical +/− buttons while locked. It doesn't lock the touchscreen or any other device functions.
It's designed to be simple, for exactly these situations — fixing the volume while your kid watches videos, disabling the volume buttons to prevent accidental presses, and making sure the volume doesn't change no matter how many times those buttons get pressed.
About the Accessibility Service
OtoLock uses Android's Accessibility Service to provide the volume-lock feature. This service is used solely to detect presses on the physical volume +/− buttons while locked, so the volume stays unchanged.
The Accessibility Service is never used to collect, store, or transmit anything shown on your screen, anything you type, passwords, photos, or messages.
You can turn off the Accessibility Service at any time from your Android settings.
A small, simple way to stop things from being touched when you don't want them to be. We hope OtoLock makes video time and screen time with your kids just a little easier.

Recent changes:
Introducing OtoLock!

A simple app that locks your phone's volume buttons — handy when handing your device to a child so the volume doesn't get changed by accident.

・While locked, the volume +/- buttons have no effect
・Unlock anytime with your 4-digit PIN
・No screen content, input, or personal data is ever collected
・Available in Japanese and English

We'd love your feedback — just use the Contact form in the app.