When listening to a phone call on an iPhone, you may have difficulty hearing the other party. However, there are a few things that you can do to make the other party's voice louder on the iPhone, such as turning up the overall volume of the phone, switching to Speaker mode and ensuring that nothing is covering the iPhone's speakers. Unfortunately the other party's speaker volume limits the volume of your voice.
Press the "Volume Up" button, located along the left side of the phone, while on a call. The "Volume Up" button has a "+" icon on it. A speaker icon will appear on the screen with a volume level. Continue pressing the "Volume Up" button to raise the receiver's volume to its maximum level.
Press the "Speaker" button on the touchscreen while on a call with another party to activate the iPhone external speaker. The external speaker is much louder than the receiver. Control the volume of the external speaker by pressing the "Volume Up" (+) or "Volume Down" (-) buttons while Speaker Mode is active.
Remove anything covering the speaker or receiver to make the voice louder. If you have an external case or have anything in front of the receiver or speaker, it could make the volume sound low or muffled. The receiver is located at the top center on the front of the iPhone and the external speaker is located along the bottom edge of your iPhone.