Are Both Bottom Speakers Supposed to Work on the iPhone?by Tyson Cliffton
The iPhone looks like it has two speakers along its lower edge, but only one of those is actually an external speaker -- the other is a microphone. Having an understanding of how the microphone and the external speaker works will help you identify if you're having problems with them.
The small group of holes to the left of the Lightning connector on the bottom of the iPhone covers the phone's microphone. This microphone picks up what you say during phone conversations so your phone can transmit that audio to the person to which you're speaking. As a result, no audio comes out of this speaker.
The small group of holes to the right of the Lightning connector is the device's speaker. This speaker plays incoming audio when you turn on your iPhone's speakerphone. It also plays any audio associated with audio clips you are listening to or video you are watching on your iPhone if you don't have headphones connected to your device.
If you call someone and that person can't hear you, whether the speakerphone is enabled or not, it's likely that there's a problem with the iPhone's microphone. If your device is still under warranty with either your cellular data provider or Apple, contact the warranty provider and inquire what the steps are for resolving your problem. Additionally, if your device is no longer under warranty, take your device to a local Apple Store or to a certified Apple repair person and inquire about the steps you can take to fix your problem.
If the iPhone's speaker starts to sound muffled, noisy or stops working, the speaker may be blown out, disconnected from its power supply or defective. If your device is still under warranty, contact the warranty provider to see how you can get your issue resolved. Alternatively, contact an Apple-certified repair person to see what can be done to fix your problem.