For all of you Boom Mac Volume Booster users who have lost your sound in one speaker, headphone or both, I have the fix.
I've been using Boom Volume Booster for some time now. Used it on my Macbook Pro and now on my iMac. The other day I noticed the sound in the left speaker in my Sony MDR-7506 Professional Series headphones fading in and out. I thought it might be the Headphones, after all, they are 8 years old. Then I thought, maybe it's the microphone jack. Then I remembered, Boom is software that pushes your default sound to the outer limits. The Boom Mac Volume Booster program places kernel extensions & audio plugins in the system, according to the the support team at Global Delight.
The Fix: Uninstall Boom from your applications folder. Then reinstall the app by going into your trash can and selecting "Put Back". I'm sure after downloading fresh copy from the website and doing a fresh install would work too. If you are not familiar with Boom, definitely give it a try. http://www.globaldelight.com/boom