With whistles it must be said that the bigger the size the bigger (louder) the sound created. IF proper design principles are followed of course. There are a number of safety whistles out there such as the FOX 40, that are very durable plastic and thus corrosion proof which give a very loud two toned sound as required by marine regulations. Great if you are lost in the woods AND if you did have it with you.
The main problem with all these emergency whistles is one of size, sure they fit in a pocket but are not really comfortable to carry around. Hung on a keychain they just take up too much space. This is where the very small and light whistles can prove very useful due to the small size & light weight. Aluminium whistles, of the same size as Titanium ones will actually be lighter and while not as strong they still hold up well on a key chain.
The advantage held by a titanium whistle is one of corrosion resistance.
A titanium whistle that is 3/8” in diameter, a bit over 1 ½” long, weighing one third of an oz, and with a lanyard hole is produced by clip-money.com. The resonance of titanium and the small internal sound chamber produces a very high frequency whistle sound.
Still loud if blown properly and the high frequency sound waves do travel a long way and are very distinctive. There are some reports that this high frequency sound may actually repel bears in the wild and are likely to be painful to dogs you might encounter on city walks. The real advantage with these is that either hung on a key chain or on a ball chain around the neck they will be handy when you need them.
Blowing one of these very small whistles does take a tiny bit of practice. Too slow a breath, trying to make a weak sound, can “choke up” the sound chamber. A sharp short and forceful breath with the lips just around the end of the whistle will make a sound more than loud enough to cause ear pain if inside a room.
I would love to hear actual reports of the use of this kind of whistle in scaring away dogs or other animals.