How can I fix a low speaker volume problem on my iPhone 6s? I have a 6s with iOS 9.3x installed. Out of the blue, the speaker volume became barely audible. By speaker I mean the the loud speaker at the bottom of the phone.

I've used headphones and bluetooth to see whether those are affected as well - those continue to work fine.

I've done the following - none fixed the problem:


Restarted the unit multiple times.
I've cleaned out the speaker and headphone jack.
I've blown compressed air at the problem spots.
I've toggled Settings/General/Accessibility/Phone Noise Cancellation and Hearing Aids options.
Various miscellaneous things that I've read about here and there.


I know that if I take it to Apple store, they will suggest restoring a new phone, which I don't want to do. Other than reinstalling the OS, what else can I do to try and fix this issue?
Answering my own question.  

Got it fixed. In case someone else has this issue, I took it to the Apple store. Turns out the speaker got clogged with microscopic particles (lint, sand, etc...) since I spend a lot of time outdoors. They have a very fine brush that can get those things out. The whole process took like 5 minutes.