I can't imagine going to the races without hearing protection, much less access to the team communications. I recently did a review for a race scanner (see comments below for the link). This is the headset I use at auto races. I purchased these due to my frustration with my first pair of headphones (review pending).
* These headphones are very comfortable to wear OVER a ball cap. Basically the support arm goes behind the head and then two a Velcro strap connects over the top. Extremely easy to adjust to fit someone with a smaller or larger sized head.
* The volume button knob on the side of the earmuff is basic but allows the listener greater control; this is especially useful if you are using a splitter to share a single scanner between two different listeners. It is easier to control the volume with this larger knob than the small thing on my scanner.
* This has a 20dB noise reduction. I wish it blocked a little more noise, but these are do produce a comfortable listening environment.
* Other than my wish for a little more noise reduction, my only other frustration is the muffs are a little hot especially in 90F+ sun.
note: these are not stereo headphones -- mono only