You'll probably notice it if you crack your windows and floor it (while obeying pertinent traffic laws of course).

 

I remember when BMW intorudced this with the Harmon Kardon system. They called it VSSE or Vehicle Speed Sensitive Equalization. You can totally tell with those systems. I am surprised the OEM system in the IS has this, I thought it was only ML. I thought I read that the base stereo had it and I was seeing things.

 

the system raises the volume only when the volume is below 50 and the closer to 50 it is the less effect you will see. try it on about 10 and you will notice a significant difference. it is speed dependent up to about 65 mph untill all the bars come on.
you will find that if your going 50 and lower the volume then raise it you will see the bars come and go.
there is no need for the ASL when your volume is up loud as its purpose is to compensate for road noise.

 

Does anyone know where the ASL take the sound measurements from? Like where mic is located? Is it the same mic as the Blue Tooth handset?

 

My experience w/ ASL on the non ML / Nav is that it lowers the volume a bit when I have it cranked. I haven't messed with it a lot but it seems occur regardless of ambient noise or speed. I leave it off.

My 3 Series BMW had it and it was much more pronounced, depending on speed.

My Ford F150 has it and it works well, especially because the interior noise is much louder in the truck. It's also adjustable in ten increments.