If your vehicle is showing horn sounds weak, muffled, or distorted, here are the most likely causes and the parts you'll need to fix each one.
Because horns are typically mounted behind the front grille, they are highly exposed to the elements. Water, mud, or bugs can get trapped inside the horn's trumpet, restricting the diaphragm and causing a muffled or gurgling sound.
Horns often rely on their physical mounting bracket to provide an electrical ground to the chassis. Rust or corrosion at this bracket or the wiring connector causes a voltage drop, starving the horn of the power it needs to sound fully.
Over years of use, temperature fluctuations, and vibration, the internal electromagnetic coil or metal diaphragm can simply wear out or crack. This results in a weak, distorted, or 'sick goose' sound.
If the horn was recently replaced or moved during a bumper repair, it may have been mounted with the trumpet opening pointing upwards. This allows it to catch and hold rainwater, quickly ruining the horn.
The relay that switches power to the horn can develop pitted or burned internal contacts over time. This creates electrical resistance, preventing the full 12 volts from reaching the horn.
If the vehicle's battery is dying or the alternator is failing, the overall system voltage will be low. The horn will sound weak, though you will almost certainly also notice slow engine cranking or dim headlights.