Problem: Missed alarms and notifications when SD card is mounted. Workaround: root your phone and move your sounds to internal memory

When you hook up your phone to your computer to transfer files, your SD card is "unmounted" and Android can't access it.

And then you receive an SMS. Or your calendar is supposed to sound its alarm to remind you of an important meeting. Or you've left your phone hanging on your computer overnight to back up your entire SD card and get your phone charged at the same time, and then the alarm clock has to fire off...

...but it doesn't.

Because when Android can't access your SD card, apps can't access the custom ringtones stored on the card.

Sometimes it will play the default tone when the custom tones are unavailable. This works for calls, but not always for messages, calendar alarms or alarm clock apps. For example, if you switch off notification sounds in Androids settings (because you don't want to hear a sound for every email or incoming IM) but enable a custom notification in your SMS app, the custom SMS sound fails if your SD card is not mounted.

Soulution: each and every app should play a backup sound from the on board memory if it can't play files from your SD card. Unfortunately there will always be programmers who forget to add the few lines of code needed for that.

Workaround: copy your custom sounds to the internal memory of your phone. This way you can unmount or remove your memory card without having to worry about missing your early morning flight because the alarm clock stays silent. Of course you need root access for that; yet another good reason to root your phone if you haven't already done so.

Always check if alarm clock apps, calendars, SMS programs and other apps play a backup sound if they can't reach your memory card. If an app fails to make some noise when it should, you should use a sound from your phones internal memory.

image from Wikipedia