Liz,
Good question. I, too, have heard some ear-splitting personal alarms, and they are very impressive.
I think that personal protection alarms have some drawbacks, though. For one, they can lull someone into a false sense of security. For another, their effectiveness does depend on whether or not they will attract sufficient attention, and whether or not anyone in the area is going to have the backbone to do anything about it. It is a shame that there are people that will stand by and allow someone else to be attacked, but it happens. Also, even if someone is around that can do something about it, there is a question of whether they can get to you fast enough to do any good.
I don't think that personal protection alarms need to be ruled out altogether, but they are among many options available to you, and should be considered as part of an
overall strategy. The key is having a realistic, workable, personal protection strategy.
Criminals do not typically strike at random. They usually pick their targets based on their observations. You might be setting up yourself or your home to be a target without even realizing it. Many people do so every day. You might find it worthwhile to learn what it is that the criminals look for in selecting their targets, thereby reducing the likelihood of setting yourself up. I would strongly suggest that you look into attending NRA's excellent
Refuse To Be A Victim crime prevention seminar. While you are at this site, you can check the schedule for seminars in your area. It is not expensive, and the stuff you will learn there is worth its weight in gold. There may well be other seminars that are just as informative, but I have attended and taught the
Refuse To Be A Victim seminar, and can vouch for its value.
If you choose to make a firearm part of your personal protection strategy, I would strongly recommend the following excellent books for you to read: Armed and Female, by Paxton Quigley; The Concealed Handgun Manual, by Chris Bird; and two books from the NRA: The Basics of Personal Protection and NRA Guide to the Basics of Personal Protection in the Home. These books are all easy to read, and you'll glean a ton of useful info in no time.