high db, high frequency

While not exactly a "car audio" application, I am using a basic car stereo setup to produce loud, high frequency tones (around 20 kHz) to deter foxes from entering bird nests (I work for non-profit wildlife organization). The problem is that I can't seem to get the system very loud.

I’m using a 12V battery and 3', 8 gauge cables with a 60 A fuse on the (+) to a Soundstream Stealth STL2.350 amp. My input is a simple tone generator. I had a Pyle Pro PDBT68 3" bullet tweeter (4-8 Ohm, 114 sensitivity, 2-25 kHz, 1200 W peak power, capacitor on (+) input used instead of crossover), which I got to about 80 dB at 20 kHz (90 dB at 10 kHz, full input) from one of the 2 channels. In an attempt to increase the dB's, I bridged the speaker, but got about the same dB level and, after a minute, a fried speaker. I have since learned that 1200 W peak power, probably means about half or less RMS and that a continuous tone will also burn tweeters quickly.

Can I get a system like this up to around 130 dB at such a high frequency in ~ 3 second blasts from a tone generator? If so, what is the best way, without breaking our non-profit bank?

PS. I am using a high quality Casella sound analyzer on the speaker axis, at 1 meter.

You work for a wildlife organisation and want to subject surrounding life to damaging audio in an attempt to deter one high-order species?
This is Christmas - not April!!!

Not that your method is practical anyhow, but I cannot support such an environmentally irresponsible realisation.

Try using some "natural" fox sounds or other deterrents instead.
Maybe localised triggered "pocket" dog chasers.

The SPL you measured from that Pyle tweeter is about right at those frequencies.  There are some other piezo supertweeters from companies like Motorola/CTS (look at their model KSN-1165) but you are unlikely to be able to generate much greater than 90db @ 20KHz with one tweeter.  In fact, most of the commercially available sonic pest repellent devices seem to operate at about 90dbSPL (such as this one.)  If you are serious about generating very high SPL, you will likely need to build a line array of super tweeters like the CTS model - or the Pyle you tried.  For example, driving a dozen of the CTS drivers with your 350 watt amplifier will generate approximately 140dbSPL @ 1 meter.

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I like your idea of using natural fox sounds.

Our intent, of course, is not to damage foxes (and feral cats') ears, but to deter them from attacking the nest of an endangered species. As you probably know, the dB level would drop off significantly a few meters away. We just want them to be annoyed enough to not enter the area. We are trying to test this system.

Any ideas about how the sound system might work best?

Thanks, DYohn, for your sound advice. I had considered using more speakers, but didn't know it would boost the levels that much! I'm guessing I would use the left and right outputs with an equal number of speakers on each one and make sure they are connected with the same length of wire? Do you know where I could find a diagram of how to connect all the speakers in phase?

wildlife amon wrote:

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Thanks, DYohn, for your sound advice. I had considered using more speakers, but didn't know it would boost the levels that much! I'm guessing I would use the left and right outputs with an equal number of speakers on each one and make sure they are connected with the same length of wire? Do you know where I could find a diagram of how to connect all the speakers in phase?

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As long as you make sure they are in electrical phase (+ and -) then you will be good.  Even four drivers with 93db sensitivity will boost the levels to around 128dbSPL.  If you used four of the Pyle tweeters you started with, you should be able to hit closer to 140db.  This is a peak number, by the way, assuming the amp is operating at 350 watts.

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wildlife amon wrote:

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Our intent, of course, is not to damage foxes (and feral cats') ears, but to deter them from attacking the nest of an endangered species.

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I was thinking of human ears, shattered eggs, damaged insects etc.

I was tempted to ask what was out of balance to see if that could be addressed - eg, here we would eradicate the foxes(an introduced species).
I'd probably supply substitute eggs or meat else somehow put the endangered species under protection.

But local environmental people should have the right answers... (Hopefully practical and not "academic" ones.)