One of my birthday presents was a little gadget named the Yakumo VolumeMaster. This unit will keep the sound volume of your TV set at the same level when advertising/commercials are broadcast.
A terrific improvement, I must say.
For all TVs with Euro AV connector (also known as SCART)
Don't know if this works in the USA.

http://www.yakumo.com/produkte/index.php?pid=1&ag=VolumeMaster

US TV can use this;
http://www.tvsoundregulator.com/
Invented by a ex Sony engineer

Terk offers this;
http://www.terk.com/vr_1.html
These are known to be sensitive (damaged) by voltage spikes (lightning). No internal MOV.

Some US TVs claim to offer sound regulation built in but it only works on the RF input, not on the AV jacks.
The Samsung DVD V1000, combo DVD, VCR had the option of sound regulation. Don't know if it is offered on other models

As unpopular "sound volume manipulation" is you would think it (sound regulation) would be built into all AV equipment by now.

P/S

Happy birthday.