sound in firefox but not chromium or music player

[fox]

I am using Linux Mint 18.3 cinnamon on an iMac, and everything is great except for sound, which works regularly if I play a youtube video on Firefox, but if I do the same on Chromium I get an error message ("An error occurred, please try again"). I wouldn't care about that so much, as Firefox is working well for me, but the real problem is that I'm not getting sound out of my music player, whether I use rhythmbox or VLC or clementine. To be more accurate, I have tried altering the settings in pavucontrol and other tricks like reinstalling pulseaudio and/or alsa. Occasionally I get the sound working in a music player by doing this, but it disappears on a reboot. I also have Ubuntu 16.04.3 installed in another partition, but I get the same problem there.

The kernel I am running is 4.8.0-53
Sound card information from inxi:

inxi output from Mint 18.2.odt

I'm wondering if pulseaudio is the problem and if so, how can I disable it and still get audio through Firefox?

Thanks in advance. I'm pulling my hair out on this one.

[fox]

I borrowed a usb sound dongle from a friend and plugged speakers into it. If I then select usb speakers in the sound app, the problem disappears. Intereestingly enough, when I plugged same speakers into the headphone jack rather than the sound dongle, I got no sound. So I have a solution, but still no understanding as to why my internal speakers aren't working with any audio app.