How to check Ultrasonic Sensor Actual Response Time

Hi, I'm working on the usual obstacle detection using HC-SR04. Basically, when an obstacle is detected around 0-60cm, the robot will response . Obstacle detection is just a part of my study. My professor requested me to measure the response time. Meaning, the time difference between detection of the hc-sr04 when detect the obstacle around 0-60cm. I know it's less than a second. Does anyone know a thing or two on how to do it? Thank you.

If you need anything like the code, photo, or whatsoever, just tell me. Thank you again.

Hint: it's using ultrasound.

Now what's the speed of sound?

You have access to a scope in the lab, use it it will measure it very accurately. You can also measure the response time of the sensor and add that as a bonus.