Why is my tablet making a high pitch sound after unlocking screen?

[Android Central Question]

I recently bought a lenovo tab 3 10 business. There are times when you will hear a high pitch sound (sounds like the mosquito repellant app) for about 4 secs immediately after swiping the lock screen. Its not a notification sound. Already did factory reset so there are no 3rd party apps. I noticed that this happens when the device is kinda low on memory..i think. This happens at random times, not everytime. NFC is turned off. When i use headphones, sound will be heard at headphones. Hope someone can help me. Thanks!

 

[B. Diddy]

Welcome to Android Central! That doesn't sound normal at all, and you've already done all of the troubleshooting that I'd suggest. Bring the tablet back to the store and ask for an exchange or refund. If it's too late for that, contact Lenovo for warranty repair/replacement.