Sensitivity adjustment on ultrasonic sensor

Hopefully this hasn't been answered already. I've done some searching and, found limited information on the question. I contacted maxbotix tech support, and they told me that I either need to purchase a different sensor or send mine in to be reprogrammed.

I'm working on a little auto ranging distance measuring device, and I'm trying to figure out how to reduce the sensitivity on my maxbotix hrlv-ez0. I had the idea of using one of the pwm pins to lower the voltage down to 2.5v which according to the beam patterns Maxbotix provides will reduce the sensing cone.

I was reading documentation on another ultrasonic ranging system, and they have a sensitivity setting that ranges from 5% to 100% in 5% increments. They say you can reduce the sensitivity for small rooms, or pump it up for targets that are wearing absorbent materials like wool sweaters. Does anyone have any idea how they are pulling that off? Here is a photo of the adjustment:

I read in the guidelines I should post the board I'm using. I'm building the project on an Arduino Micro with the MB1003 sensor.

Thanks for your help!

bump 8)

I have seen variable gain implemented in the receiver portion of things like depth sounders before, so I know it has been done with the right transducer, but that requires you to handle the raw signal from the transducer to accomplish that.