I'm trying to set up a deterrent system and after a lot of thought I think I've figured out how to do this. This situation is fairly unique so I'm afraid suggestions other than the path I'm pursuing probably wouldn't apply. So I'd like to keep the discussion on the right path if at all possible. My goal is to create a continuous stream of air that would blow into an Aztec Death Whistle. Youtube it if you haven't heard one. The audio doesn't nearly do it justice. The 'whistle' takes a good amount of breath to get going. A full set of lungs only gets about 3-4 seconds out of the thing. What I've found to be a good source of air for the whistle is my 18v battery powered Ridgid small shop blower, using the smallest 2Ah battery. It's a small blower about 18" long. The whistle's full volume may be reached using somewhat less air than this blower on full, but that's generally the volume of air I'm talking about. This blower isn't designed to run continuously so another style of air mover would have to be used for the final model.

The requirements are that the system needs to be able to run on both house electric or battery power. Normally it should run on house power, but if the electric gets shut off it will switch to battery. I'm hoping to get some kind of battery setup that'll keep it running for about 2 hours before it runs out. The last requirement is that the whistle should not be heard to vary in tone at all if the house elec is shut off and the device has to switch to battery.

Sounds devious huh?

Any thoughts?

 

You need to look up the specs on your blower to see the pressure and CFM that it produces.

Then start looking for blowers of comparable flow capabilities that are rated for continuous duty.

Then use its power requirements to size a suitable set of batteries.

Then, to have the best shot at meeting your last requirement, power the thing from the batteries all the time but have them being float charged from the AC. That will keep the batteries always ready to go and the actual power being used under normal conditions will actually come from the charger (so it has to be rated to deliver that amount of power continuously, of course). But then there's the issue of what it means for the tone of the whistle to not change at all. What is the metric of what constitutes not changing "at all"? As the batteries drain, there will likely be a change, but whether it meets your needs (as opposed to your wishes) depends on what your needs actually are.

Another approach is to use a UPS. You will have to run tests to determine if it meets your "not change at all" requirement, since the output waveform is almost certainly going to be somewhat different than the house AC power, both in terms of frequency and harmonics. Whether or not that translates into the air delivery to the whistle changing "at all" is that it almost certainly WILL change it -- but it may not change it enough for anyone to notice. It all comes back to quantifying what "not change at all" means.

 

I YouTube’d it, and you are right, it is a beyond creepy sound if it is modulated correctly.Similar to a child screaming with pain.
I don’t know if a continuous tone would achieve the same effect.
As a fact of the several Youtubers demonstrating it, IMHO only one created a truly hideous and creepy sound.

 

You may want to look at a device like this, meant for blowing up air mattresses and other inflatables. It moves an incredible amount of air at relatively (to a tire pump) low pressure. Rechargeable battery, AC adapter. But I don't think it's meant to ever run off the adapter. Maybe it could if the adapter had enough capacity.
Anyway, maybe worth a look. BTW, they make a fantastic fire starter when camping at higher elevation.
https://www.amazon.com/gp/product/B07QBMQSMS

 

There are air mattress pumps that are AC powered only and others that will work off either. But I don't think any of them come close to moving the kind of air that a shop blower moves, but that's just a gut feel more than anything.

 

The Aztec Death Whistle sounds are played on You Tube and the sound is awful.
Amazon sells a few different copies of it.