How Do I increase the call volume on my Samsung Galaxy S4?

When you are on an active call, you can adjust the call volume with the dedicated Volume keys on the side of the device. Touch Extra volume  from the active call screen to increase the volume level. When the feature is on, the icon will appear green . If the audio quality is still not what you would like it to be, you can touch Noise reduction  to turn off the feature.

Personalise Call Sound

Touch Phone  > Menu  > Call settings > Personalise call sound and choose from Adapt Sound, Soft sound, Clear sound, or Off.

If Adapt Sound is selected, the device will guide you through customising an optimal call sound. Before starting, it is recommended you close all multimedia applications, be in a quiet environment, and have a compatible earphone connected. The device will play a beep; touch Hear if you hear the sound. If you cannot hear the sound, touch Cannot hear. Once completed, touch Done to save your personalised call sound.

To enable the Personalised call sound, on an active call, touch the icon and touch Adapt Sound.

Note: please disable the Extra volume feature and disconnect any earphones prior to using the Personalised call sound option. You can also access call settings from the Home screen. Touch Menu  > Settings  > My Device  > Call  .