I want to use dfplayer modules speaker output to connect to SIM800L MIC IN Pins. Can this being done? How to connect it? In other words Instead of a MIC input on SIM800L module, I use the sound out of the dfplayer module. Please see the attached file.
What is the reason for the noise? How can I fix the noise? Can you guide me by schematic?
I tested the following items according to the picture, but there is still noise
You would have to check the specifications for the SIM800's MIC input.
As it's called "MIC", it's probably expecting a microphone, which is a very low level input - much lower than a speaker! 
What noise? You didn't mention any noise.
Can you guide me how to convert the output of dfplayer to the required microphone input of sim800l?
The link to download the noise sample has been created
Have you looked up what that is yet?
You have completely misunderstood the issue
Can you help me how to output the sound of the module
Dfplayer
to the microphone input
Sim800l
connect? Guide by map??
No, I haven't.
Fundamental to connecting any two devices together is to know the specifications of those devices.
You need to know the MIC input specifications of the SIM800 in order to feed it correctly
You also need to know the output specifications of the DFplayer
So - have you looked them up yet?
The two most noise generating devices you have in that setup is the two buck converters. For lower noise you need to replace them with linear voltage regulators,
Second you have no biased AC coupling going into that chip from the speaker outputs of the DFplayer. That will cause severe distortion of the audio signal which you might be mistaking for noise.
Third your signal is probably way too big anyway.
I am a beginner, if you can help me please, if you can't help me, I will thank you again
But you are not doing a beginners project. And I suspect you don't have the measurement equipment like an oscilloscope so you know what your signals are doing.
I have told you what you need to do - look up those specifications.
Search for the datasheets for those devices.
The audio interface circuit below is right idea, but try C1 = 1 uF and R2 = 47K or even 470K to avoid overloading the SIM800 microphone input.
Also follow the suggestion above to use linear voltage regulators instead of switching regulators to power the components.
For voltage supply
Sim800l
And
Dfplayer
from the module
LM317
Is it appropriate to use it? I sent a photo of the attached module
Thank you very much, I will check the method you said
Well no given that you show one module needing 5V and the other needing 3V3. How is that going to happen?
Using two modules
LM317
I set one to 4.2 volts for sim800l
and one 5V for
Dfplayer
I use 9V switching for the power input
Connect two LM317 modules with Arduino
Is there a problem??
What does that mean exactly? What is 9V switching?
I did this method, the hissing increased, it is completely hissing
dfplayer music sound
Nothing is played
What method?
The audio interface circuit below is right idea, but try C1 = 1 uF and R2 = 47K or even 470K to avoid overloading the SIM800 microphone input.
?
