Interesting, I have always wondered why survival whistles have become so high pitched over resent years. Especially as it has been know for around 100 years that low pitched sound travels a lot further than high pitched.

This was shown in a very practical test when researching the improvements of nautical sound signals and foghorns. I don't remember the chaps name but he had a piano placed on a beach and different notes played whilst he sat in a rowing boat seeing which note was heard the furthest. He reported that the low notes could be heard the furthest and this was adopted for use in foghorns.