If you have a headset that includes a microphone, you can blow on it (this is also known as an external microphone). Otherwise, simply use the internal one.
The internal mic is usually at the back side of your device, in terms of the side farther away from you (in portrait). In landscape (Home Button to The Left), it will be on the right side of the device.
If it is facing Landscape (upside down), it will be on your left. If it faces portrait (upside down) it will be in the front closest to your body.
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Blow on the microphone
If you have a headset that includes a microphone, you can blow on it (this is also known as an external microphone). Otherwise, simply use the internal one.
The internal mic is usually at the back side of your device, in terms of the side farther away from you (in portrait). In landscape (Home Button to The Left), it will be on the right side of the device.
If it is facing Landscape (upside down), it will be on your left. If it faces portrait (upside down) it will be in the front closest to your body.