There are some mobile device in the market with a very poor or medium audio quality and volume, especially some low mtk smartphones and by such one can't enjoy the audio quality of his device. I will always rate HTC smartphones very high in terms of audio and volume clarity.
If your mobile device has a very poor sound quality or the volume is very low especially without the earphone, there are some apps that will help to boost the audio quality of your device and enjoy music with your smartphone.


[b][/b]Music Volume Equalizer:

This is probably the best music or volume booster for Android device, music Volume EQ app features a five band equalizer, media volume control, bass boost, virtualizer effects, 9 equalizer presents and more.
If your Android device has a poor quality audio then this app is must for you.
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[b][/b]Bass Booster:

Bass Booster for Android is a great looking app which shows you exactly how much bass boost you will get. It also comes with a virtualizer, which enables the app to bring audio which is crisp, as well as, carry a hefty punch to it.

There is a five band equalizer in the app along with well optimized equalizer presets and a volume dial to control the universal volume of the device.

[b][/b]Ultimate Volume Booster:

This helps to increase the volume of your device by 30% – 40%, so if you have a phone with low volume this app is for you and it increases the volume for notification sound, ringtone, alarm, and multimedia sound.
It also boost the sound quality of your smartphone not just only volume as the name implies. And also works with headset, headphone and speakers.

[b][/b]EQUALIZER & BASS BOOSTER:

Equalizer & Bass Booster provides you different preset and reset equalizers that will increase the sound of your android. You can give amazing bass and virtualized sound effects to your volume settings. With this audio booster app you can also play the videos and listen to the music or other stuff in high sound

There are other good quality ones out there but i always prefer this four. If you want to download them click on the link below.

http://www.zpykios.com/2015/07/best-android-audio-apps-boost-smartphone.html?m=1