This sound was heard on one of my summer trips. I was still in China at the time and it was a family trip. My family and I went to a faraway country town where it was so cool in the summer that we chose to stay there for a few days to escape the heat of the city. There was a very large lotus pond around the town, and it was decorated with lights, and at night with the lights on, it was a very stunning visual experience.
As I was walking around the pond with my family, I heard a sound like a man burping. It was like a bursting bubble with a low and dull sound. At first, I thought it was the sound of someone who had eaten too much for dinner and accidentally made a burping sound. As one entered the depths of the pond, this sound became more and more pronounced and more numerous. They rose and fell like a symphony. Then I realized that it might be a frog call. But it didn’t sound similar to any frog call I had ever heard, it was a call I hadn’t heard before. But since the lotus leaves covered the pond, I couldn’t even see what it looked like. Even now I am very curious about what a frog that can make such a sound looks like!