Distortion when playing 4 tracks

I have a problem that relates to distorted recordings. I’m editing 4 tracks (uploaded WAV files) recorded from a Zoom Recorder, which sound fantastic until I play them back in Audacity - then I get distortion, with a tunnel sound, volume goes in and out, tinney sound. I’ve read all the info I can find about this in the forum but I’m obviously missing something! Can anyone help? Thanks so much. I’m using Version 2.0.2 on Windows 10.

Do you mean that you are playing all 4 tracks simultaneously? (tracks imported one above the other?)
If so, then you probably need to reduce the level of each of the tracks. When tracks play at the same time, the “mix” will usually have a higher level than the individual tracks because there are multiple sounds being added together. If the sum (mix) of the sounds goes above 0 dB (as shown in the Audacity playback meter, it will overload the sound card and distort.

A “tunnel sound” usually indicates that Windows is applying “enhancements” to the audio. To turn off Windows sound enhancements, see: http://manual.audacityteam.org/man/faq_recording_troubleshooting.html#enhancements