My 11-year-old 40" Sony LCD has just such a feature. Some TVs have something called "steady sound" or something similar, which compensates for differing incoming audio levels and will ensure that there are not significant differences between channels. The only channel that causes me significant issues is Retro (703), which is a lot louder than other channels, but I only notice that on my home theatre, where I'm feeding an AVR instead of a TV. My volume was the same on all the channels.
I checked all those channels on my TV and didn't encounter anything like that. I was watching the History channel the other night and had to turn the volume up to 30. About half the channels seem to be on low volume.
When I switched to CBCNews 26, I had to dial it up to 21 to hear it as well as I could the other channels. If your computer is getting Internet connection, you may proceed to the next step. One CSR and one tech said the signal we're getting is weak but no one seems able to do anything to boost had my TV's volume at 14 for CP24 and CNN this morning and could hear everything fine. Connect the computer to the Cable modem using an Ethernet cable. Mentioned this to Rogers and they've sent three techs. We have a Cisco 9865 PVR, so no volume button on the front panel. We have two TVs and the problem is happening on both. CP24 and CNN (and some others) are fine at 14 or 15 but CBCNews channel and others need to be cranked way up between 20 and 30. Your devices power on or off simultaneously. Press the source button for the device that is out of sync.
Use the following steps to resync your system. For instance, watching the History channel we had to put the sound up to 40 when anyone was talking low. TV may become out of sync and not power on/off simultaneously. I set the audio output on the box to PCM only instead of Dolby, and suddenly the tv kept sync (I still had to set the sync settings on it, but prior to that, I'd do so, and after 10 minutes it would be out of sync). I was hoping there would be some way to set the volume higher as we're having a problem with volume on some channels. It turns out the issue appeared to be my cable box, not the TV. Keep the Audio Range to "NARROW" for the loudest possible volume - any other setting (especially WIDE) will make the volume lower than normal (except for the explosions/loud booms). Press and hold the "VOLUME +" button on the front of the PVR (front left) until the volume is at max (see TV).