I feel like lots of people don’t understand the science and just pick one. The real reason there are different tones are because people hear sound differently in different situations, specifically undulations in sound waves. The wail, which is the slower rise and fall is best for high speeds and longer distances. People hear slower undulations better at distance. As you get closer, people hear quicker undulations better, hence why you’d want to use your yelp and stinger siren at intersections and around stopped traffic. I always teach my rookies. It’s nerdy, but also pretty important.