Problem of Ultrasonic sensor

Hi everyone,
I have changed 2 new ultrasonic sensors already, but I have faced one problem is when i start detecting the obstacles, the ultrasonic sensor will late a bit just start detect the obstacles.
So, my question here is, is that normal situation for ultrasonic sensor that will delay some time for starting detect the object.

Many thanks here.

There is most likely a problem with your program, which you forgot to post.

Please read and follow the directions in the "How to use this forum" post. Post the code, using code tags, and a wiring diagram.

Then there's also the time the sound waves take for a round trip...

How much of a delay do you experience, really? What is "a bit late" in actual numbers?