Make sure you have plugged correctly your headphones to your phone with Headphones Indicator. This app sends notifications every time you plug your headphones, so you can be sure that they are correctly plugged and and the phone speaker is not goig to play anything. This is nice when you are in in places like a library. You can also disable the notifications if you want.
Get the .apk file of Headphones Indicator 1.3.1 for free and have a look at users' reviews on Droid Informer. The installation package occupies 2 MB on disk and it works flawlessly on Android 1.5 and above. According to the antivirus report, the app doesn't contain viruses or any kind of malware. Susomena is the creator of this application which can be found in the Tools category.
Over 100K users downloaded and installed Headphones Indicator and its latest update was on Mar 9, 2015. The app has the overall rating 3.2 on Google Play. Advertisements are a part of this application.
Some users are of the opinion that you can get such an advantage of Headphones Indicator as great customer support.