Acoustic impulse response for ultrasonic simulations

Hello,

I am currently trying to simulate the behaviour of an ultrasonic sensor for simulation of Autonomous driving systems.

I think I will do this in three steps:

1) transform input voltage to emitted sound wave by known transfer function of transducer

2) transform emitted sound to reflected sound by convolution with environment impulse response

3) transform reflected sound to received voltage signal by known transfer function of transducer

I have some questions about step 2:

I have found the following image in "A real-time capable multi-sensor model to validate ADAS in a virtual environment"

Each object seems to generate a skew "pulse" of around 5ms wide which I have approximated by an inverse gaussian as a quick test.

The problem is that when convolving this impulse response with a 58kHz sine burst, the sine gets filtered out (thus no sound returns to the transducer). This impulse response is continuous while most images I find on the internet first have a few individual dirac pulses before the continious part. When I approximate the response by just a series of 4 scaled dirac impulses the reflection is as expected: a series of scaled and delayed sine bursts. I gues i'm making some obvious mistake or don't understand the impulse response method properly ?

Kind regards,

Lennert