Remove startup/shutdown sound of TECNO N3.

Introduction.

There does not appear to be any application that can turn off the shutdown sound for a phone in it's factory state. The best you can do is select Sound OFF when you do the long press to turn the phone off, then do the log press again to actually turn it off. There are applications - Android Assistant for instance - that will suppress the startup sound. The snag with this approach is that you have to remember to turn the sound on again when you restart the phone, which I always forget to do.

This annoyed me sufficiently that I rooted my phone so I could fiddle with the responsible files. Rooting is itself non-trivial. I used the approach suggested here.

I figured that not finding the startup file might cause a problem when booting, so I replaced it with a short mp3 of silence. The shutdown sound I simply removed.

Nitty Gritty.

After you're rooted, you'll need to install a terminal emulator on your phone. There's one surprisingly called Terminal Emulator in the Google app store. Once you've done that, open it, and enter the following sequence of commands (don't enter the parts after ';' - they are just comments.) You'll need to do this very carefully, especially the mount command. If you get anything wrong, it won't work.

Put your silence file - say silence.mp3 into some convenient folder on your SD card using ADB or just using the USB cable.

$ su                               ; request root access
# mount -o rw,remount -t yaffs2 /dev/block/mtdblock1 /system   ; mount the system directory as read/write
# cd /system/media                 ; change to the system media directory
# ls                               ; list the files there
At this point you should see:
bootanimation.zip
shutdownanimation.zip
audio
power_off.mp3
power_on.mp3
Rename the power_on.mp3 and power_off.mp3 files to old_power_on.mp3 and so on using:
# mv power_on.mp3 old_power_on.mp3
# mv power_off.mp3 old_power_off.mp3
Now move the silence file into the /system/media folder, and rename it:
# mv /mnt/sdcard/silence.mp3 /system/media/power_on.mp3
Check the listing - should now be like:
# ls
bootanimation.zip
shutdownanimation.zip
audio
old_power_off.mp3
old_power_on.mp3
power_on.mp3            ; this is now silence
Get out of the terminal by typing
# exit
$ exit
Then shut down the phone. That should now be mercifully silent. When you restart, the /system directory will be mounted read-only as usual, but there should be no startup sound.
This should work with other Android phones if you first use a file manager to determine the location of the files that store the sounds. The mount command will likely also need tweaking. Run mount without arguments:
# mount
...
/dev/block/mtdblock1 /system yaffs2 ro,relatime 0 0
...
...

It will show many lines represented here by the ellipses. The line shown is for an N3. Your /system line may differ. Substitute what you see in columns 1 and 3 (/dev/block/mtdblock1 and yaffs2 here) in the remount command.