I think this refers to the second ding (at 10k ft?)

I lost a couple of classmates on SR 111 and spend about 10 years as a very nervous flyer. I used to really find comfort in the dings followed by cabin crew reminding you that smoking was not allowed etc. I had quit smoking by that point so wasn’t directly relevant to me but I reasoned that if we were imminently about to plunge to our deaths then nobody would be calmly making such an announcement.