Thanks xD
Humm thats a good idea and probably will work and like you said i'm don't want to use individual ultrasonic transducers.
I did some more search and found the LV-MaxSonar®-EZ0 (Ultrasonic Range Finder - LV-MaxSonar-EZ0 - SEN-08502 - SparkFun Electronics) that seems very good for the project i want to do too.
This ultrasonic from what i see in some examples posted, with some synchronization can be used in my project (one transmitting and another one receiving).
What do you think?