Hi everyone, I don’t really know how to use this forum well, so I’ll get straight to the point. I had bought two audio cassettes from eBay, and when I played them in my cassette player, something sounded off. There is a buzz in the audio, but I’ve been reading reviews of my cassette player, and when people had the same problem, they said to buy powerful batteries instead, but I use Ikea rechargeable batteries, so maybe their not powerful enough. But the main thing is the audio quality sounds so terrible for some reason. I have a sample I recorded to maybe explain better, if it’s too short, I can get a longer sample. I’m just at a loss and need help.
The main problem is there are dropouts: pieces are missing …
This can be due to programs fighting over control of input-devices, or interrupting in some other way …
https://manual.audacityteam.org/man/faq_recording_troubleshooting.html#How_can_I_record_without_small_skips_.28dropouts.29_or_duplications.3F
Yes, I think you are right! When I remove an alkaline battery from a failing device, I generally test the battery to verify that is the problem. A “dead” alkaline battery (nominally 1.5volts) will measure anywhere between 1.1 and 1.35 volts depending on the device. If they are at say, 1.42 volts, I reluctantly return them to the device and look for another problem.
Your rechargeable Ni-MH batteries are nominally 1.2volts, which means they are already “dead” for some devices. If the device works with the batteries, fine, otherwise, try those alkaline alternatives.
BTW, I personally stay away from the regular “heavy duty” batteries as I have experienced too many cases where they leaked and corroded the device I had put them in. 
Do other, non-eBay, cassettes experience the same dropouts ? 
Ok, I guess that explains why there were skips in the audio, but for some reason, I also hear that the music sounds a little scratchy or somehow not sounding clear and perfect. Maybe I’m just imagining that.
Ok, so that explains why there is a hum in the audio, so I’ll probably get some alkaline batteries from some store. But for some reason the audio sounds scratchy to me. Maybe I’m just imagining stuff.
Odds are there will be crackles where the drop-outs occur.
If the drop-outs are very brief all you will notice is the crackle where the join occurs.
Try giving Audacity “above normal” CPU-priority to lower the odds it will be interrupted by other processes.
If that does not work try Audacity’s free competitor … https://www.ocenaudio.com/
Sorry, but it still has problems even with cpu-priority set higher or using ocenaudio. I can upload another sample if need be.
Sorry, but I bought alkaline 1.5 volt batteries, and the cassette player still has hum.
If the problem is common to both Audacity & ocenaudio, then it’s either other software (Skype?) or Windows.
It doesn’t sound like a problem caused by Windows audio enhancement,
but you could check enhancements (recording & playback) are switched off … https://youtu.be/sxnUjiGgBaI
There is no hum on the audio you posted. If you can hear hum on it your playback device is adding it.
(If they are home-made recordings it’s possible there is mains-hum baked-in when they were created).