I have decided that since my present car horn is not working properly, I will replace it.  But I want to replace it with a much louder horn that will not require any extra mods or parts.  Meaning, still using the 12v supply and no extra air compressor.  
Does anyone know how loud in decibels (dB) and what frequency (Hz) the stock horn on a 2002 2.4L Z24 is?
Thanks
radarcav
 
not loud at all... get one of those ahooooooga horns..
 
Yeah I saw those.  I was thinking more like the following (each around $30 CDN):
El Grande Twin Red Electric Horns 
This electromagnetic horn was designed and engineered for a loud and harmonious sound 
Available with dual high-low configuration 
Steel housing with plastic cover and projectors 
Copper wire coil motor 
Exceeds SAE and OEM specifications 
130 decibels 
405 Hz low/485 Hz high frequency 
Uses 12V power source 
Easy installation 
or
Freeway Blaster Horns 
Big rig sound - twice as loud as conventional horns! 
Excellent for OEM replacement or supplemental use 
Rugged steel housing and plastic projector construction 
Copper wire coil motor 
Corrosion-resistant finish 
1 or 2 terminal 
130 decibels 
Uses 12V power source 
Instructions included for easy installation
 
if you plan on using a big horn, might wanna use a relay instead of just plugging in the horn to the stock harness
 
I make those horns for a living and they are 110 db at 12.0v.
 
Dale:  
Why the relay?  I'm not sure how much current the horn (stock or new) will require but do you really think the stock wiring harness is that inadequate from a current perspective?  If I use a relay, I'm assuming you are suggesting to use the harness to drive relay's armature and then using a different fused 12V line to drive the horn.  This way if I want to honk the horn, I would push the middle of the steering wheel, the harness from the steering wheel would send the signal to the relay and close the armature and thus the extra fused 12V line would drive the horn.  I am suggesting a fused 12V line to prevent a potential short circuit from blowing the horn.
13lucky13:  
So are you saying the 130 dB is at some voltage higher than 12V?  Do you remember how much current was required at 12V to drive the horn?