For an Obstacle Detection application on a RPi 3B+, I've placed the HC-SR04 on a pair of eye glasses and as I move forward wearig this glasses when walking, it detects obstacle like walls up to 13 feet away. My associates have coded the Pi in such a way that different audio tones are generated for 13~10 feet, 10~4 feet and < 4 feet, so a Visually Impaired person can know the distance to the obstacle.

If I point my head downwards and move towards an object 2 feet high, say a chair, it detects this obstacle only when it is 4 feet away. Kindly note that I'm 5'8", so the glasses is about 5'6" above the ground.

Due to wiring constrains, I now have to place the HC-SR04 inverted (upside down). Now as I walk forward, it detects obstacle like walls up to 13 feet away but when I approach the a 2 feet high object, say a chair, it now detects this obstacle only when it is 6 inches away or sometimes the whole system hangs.

Can the SR04 be placed inverted for this application and will it work? Do let me know if anything can be done to make this work in an inverted placement?

Thank you.