Why isn't my burned CD working?

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I've had this happen a few times before when I've burned a sub onto a CD, but I've never asked.

I wished to check an old boom box's speakers (early 2000's era) for playing silent (ultrasonic) subs. So I burned the free test track onto a CD-R. It plays on my desktop PC (Win7) where I burned it, using either WMP or VLC. The CD-R is a Phillips 700MB, and I burned it with Windows Media Player. I burned an mp3.

But when I play the CD in my boombox, no sound is heard.

I turned up the sound. Nothing.
I played with the sound equalizer. Nothing.

Why won't it play? I've wished to play a silent sub on loop, yet I'm unsure why it's not working. The boombox has good speakers, both high and low frequencies, plus I'd like to be able to shut down my PC sometimes and not kill the sub playing.

I'm glad I can ask here.

You need to burn with Nero 9/10. Some cd player cant just able to play it inly with an mp3 player file itself. They need some other things.