From "Identify that mystery part", the subject of this thread has taken a curve toward the effectiveness, or not, of the deer whistle.
And, I know that since decades, with reason, there is a general concensus in the motorcycle community that they are not very effective.
Anyway... As a complement of information, you might be interested in the conclusions of an article I have just read, from Fred Rau ( a motorcyclist journalist and writer, author of the "motorcycle touring bible") about the effectiveness of deer whistle for motorcycle.
The article seems to date back from around 2010. I will give the link at the end for those interested in the complete article.
So after having tested both types of deer whistle (the most common and original "air pressure" type and the new "electric or electronic type" (as the Hornet brand ) his conclusion are that :
1- the most common air-powered type are completely useless.
2- among the new electronic type, the hornet is the most loud and by far the most effective. While other electronic whistle had make 70% of the deer react at a distance of 300 feet, the Hornet had make 82% of the deer react at a distance of 500 feet.
Now... that being said... the second part of the problem is the trickiest : once you got the deer's attention... what will the deer do ?
So... (my words here), I think we can look at it like a High Visibility Vest. Why do we wear them ? Because... we believe it helps in making us more visible. And yes, even with a High Visibility Vest, there will always be someone to say "I never saw him coming".
So, that specific brand (Hornet) of deer whistle is effective at producing a sound that can be heard by deers, at some distance (500 feet) in front of you.
And that is all it does. It says : "I'm here. And I'm moving toward you. Now, what will you do ?"
So, Yes, I'm gonna buy one, from this specific brand. But like with a high visibility vest, I will not put all my trust in it.
If it can help save my life, even only once, why not ?
Fred Rau's article can be found here :
https://dbridgerhot.blogspot.com/2013/03/deer-whistles-do-they-really-work.html?m=1