Not only does a soft reset remove bugs, but it also helps free up internal memory on your iPhone by clearing cache data.
Here's how to correctly perform a soft reset on your iPhone 7 Plus: For at least 10 seconds, press and hold the Sleep/Wake button until the red slider shows. To totally turn off the iPhone, drag the slider. Allow 30 seconds to pass. Press and hold the Sleep/Wake button for another 30 seconds, or until the Apple logo shows.
After the reboot, check to verify if your iPhone speaker is operating correctly.