Humming/buzzing sound at low acceleration

I got a Camry 99 le 2.2l
I took my car to th mechanics because of this humming/buzzing sound. I can hear in the cabin, but I am not 100% sure from where’s it’s coming from, it might be coming from the front right. It happens when the engine is warm and I am pressing on the gas pedal very gently and keep the engine at 1.2-2.0 rpm. The mechanic said it could be the alternator, because my battery was bad, I replaced the battery and it still makes that sound.
Can anyone tell me what else it could be?

Check this out. Is this the noise you are hearing? This is an easy fix

Yeah! It sounds something like that, I and gonna check if that! But the my car didn’t make the noise when when not moving. I tried to rev the engine to 1.2-2 rpm on parking, it didn’t make the noise.