If I am a film director to record the story, I would certainly choose to create the perfect quarter sound by myself to get the natural sound. However, as a journalist, I cannot betray the journalist moral standards in this situation: “Journalism’s first obligation is to the truth.”
First of all, as a journalist, I should be presenting the story objectively. I am not the character of the story; I am only a recorder. If I just drop my own change in the jar and “stage” a sound, my action becomes part of a story which influences the independence of the story. It is not an actual and authentic story anymore. While it is just a little sound that I created, I may keep creating more sounds to make the story “perfect”. At the end, I may have the “perfect” news story, but it is fake. The story loses its whole value because journalism aims at gathering, verifying and reporting truthful information.
Second, I think one of the solutions is to wait for another person to drop change as long as it is not dropped by the journalist himself/herself or ordered by the journalist. It is not unusual to wait for a long time for the perfect story. The New York photographer, Jay Fine, had always wanted to take a photo of lightning bolt struck the Statue of Liberty. He waited for 40 years to take the picture. If during that day no one drops a dollar in the tip jar anymore, I can come tomorrow to wait for the perfect sound. All I need to pay attention to is remember to record all the sounds that happen.
Third, if I do not have the chance to record the sound again, there are other solutions. I can choose to take some videos to explain what happen at the diner. I can also choose to record other sounds: the door closing when customers leave, the footstep sounds, customers calling the waiters to pay the bill, etc. There are other ways to provide a detailed news story. It is not absolutely necessary to tell the story with the sound. A good planning also needed to avoid missing the sound if it is important in the story.
In conclusion, I would choose to not drop my own change in the jar and record it. Although I may cause much trouble to myself to find other sounds, I still will not do that. As an ethical journalist, I need to present the factual story.