Honda City — wrong noise

I just bought Honda City almost two months from Submit Honda Automobile Company in Thailand. Now I have a problem. My car makes a noise "crack" when it raeched 40km/h after I started and moved for the first time. After that the noise didnot occure again without turning off the engine and starting it again. I noticed the noise will occured at the first time if I started my car and reached 40km/h. Then i can drive my car without the noise while I am driving all the way. Nowadays, I can see lots people complain and ask each other like me on some websites in Thailand, but Honda Thailand don`t care and don`t notify the customers what happen about the noise. Honda in Thailand ignored customer`s complaints.Now I worried about the problem that occured with my car. I think everyone want to get the help from Honda for analyzing what does the noise come from? and why does the car make the noise when it reached 40km/h. I hope you can reveal what happen to my car and help us with sincerely. I am looking forward to hearing from you. Thank you. Pannarat