Audio only comes out of ear speaker on top and not the speaker

[mynhidong]

Please tell us some basic information before asking for help:
Model Name:ASUS_X00QD
Firmware Version:8.0.0
Rooted or not:
Frequency of Occurrence:
APP Name & APP Version (If your issue relates to the app):
In addition to information above, please also provide as much details as you can, e.g., using scenario, what troubleshooting you've already done, screenshot, etc.
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I have my Zenfone 5 for more than 2 years now. When I record a video and watch it over, there would be buzzing sounds coming from my phone. When I pick up a call and want to put it on speaker, I couldn't hear anything and would only hear the other party's voice when it is not on speaker, however they cannot hear me and instead would hear the same buzzing noises. When I watch youtube videos, the sounds would only come out on the ear speaker which is located on top and not the speaker on the bottom. This has happened for a while. Usually before I could fix it by putting the volume on maximum and play some loud music and the audio would come out of the actual speaker instead. However, now I cannot fix it with that and can only hear sound from the earspeaker.
I feel like the speaker is broken as I have dropped my phone several times.
I hope I could get some opinions on this. Thank you in advance.

[Christine_ASUS]

Hi mynhidong
Thank you for your asking. The hardware damage caused by drops is a irreversible damage, which need to be repair by the repair center. However, you may practice some software troubleshooting before visiting the repair center:
1. Please try to enter "Safe Mode". If the function works well in Safe Mode yet the issue remains out of Safe Mode, please check on any disturbance from the installed 3rd party apps.
# How to enter and exit "Safe Mode"
https://www.asus.com/support/FAQ/1005163/
https://www.youtube.com/watch?v=Q5AJ4kNGCFs
2. Please check on SMMI test 
Calculator> type ".12345+=">SMMI TEST>Single Test>Speaker Test/Receiver Test/Headset Test

If any of the SMMI tests fails, indicating high possibility of faulty hardware, kindly bring your device to the nearest ASUS repair center for device checking: https://www.asus.com/support/Service-Center-All-Countries/
If it is impossible to access the service center during Covid-19 period, please try Call us: https://www.asus.com/support/CallUs