Q: iPhone 6 ear speakers sound distorted on phone call

Also have an issue with an vibrating earspeaker on my brand-new 6s+.

Apple replaced my phone and I noticed the same issue again.

So I investigated more and found out that the vibration is reproducible by slightly tapping on the screen in the upper right corner. It seems to come from the camera.

I went to the Apple Store and tapped nearly on every iPhone I got in my hand. Everyone was vibrating! I think that this vibration is a design flaw.

I gave my iPhone to 9 people and dialed my mailbox. Only two of them heared the vibration AFTER I told them.

I notice it only with some voices (my mailbox and my girlfriend). So I think that the majority does not even notice it as you need a good hearing to recognize it.

     Thank you so much for your help! My problem occurred from out of nowhere, and was very worried that I had severely damaged my phone. Even though my phone is through Verizon, I decided to try the steps, as if my phone were through at&t, and it worked great! Thank you for  your assistance.

IT could be the screen protector not fitting properly. If the earpiece(even the little dot beside earpiece is covered) it will make everything sound messed up or u not being able to hear at all. Even the people on the other end of ur call won't be able to hear u clearly. Also it could be a little piece of debris in your headphone jack. U need something like a q-tip w/o the cotton piece to clean it out or use a blow dryer on low heat to blow out any debris(lint,dust etc

This was a definitely problem with my iPhone 6.
Both speakers on my phone played distorted muffling sound.
It's probably due to the design architecture of 6th generation iPhones.
Dust and dirt stuck and penetrate so easy into the speakers membrane so that both speakers plays distorted muffling sound.
I used ear cottoned stick and isopropyl alcohol to clean them.
After 5 minutes of cleaning and scrubbing little by little they started again to work as new.

Yaaaaaaaaaay !