final year project: a blind stick that uses different sensors, help needed

[Hero999]

You'll probably find that just sending a 40kHz sound out through one transducer and monitoring the intensity of the reflected pulse, will give unpredictable results. The intensity of the refection will depend as much on the shape object and its composition than its distance. For example you have two objects, one made of foam and the other from steel: the steel object is reflects sound and the foam object absorbs sound. If you placed both objects the same distance away from the amplifier proximity sensor, the absorbent object will appear to be a much further away than the reflective object.

This is why you need to measure the amount of time it takes for a pulse to be reflected off an object to gauge its distance, simply measuring the intensity of the reflection won't work. As I said earlier, if you want accuracy you'll need temperature compensation and for real accuracy air pressure compensation, although this is probably overkill for what you want.