According to news reports, Caltrain has had to make its horns even louder, to comply with counterproductive FRA regulations. It used to be that states and local jurisdictions had control over the amount of horn blasting, until the FRA Federalized regulations in the late 1990s. The horn blasting has made it more difficult to implement Transit-Oriented-Development near rail lines, because nobody wants to live near a noisy neighbor.
Here again, the FRA approach to rail safety is polar opposite to the European approach. Typical operating practice in Europe is to only sound a horn in an emergency, or at unguarded railcrossings. For protected crossings (with gates and bells, etc), there is no need to sound a horn. Indeed, sounding the horn gives false sense of security and over time can lead people to venture onto tracks if they can’t hear the horn.
Here we see a Dutch intercity train at a grade-crossing:
Note that proposed grade-separation for Caltrain (as part of the CA high-speed rail) won’t entirely fix the problem. The FRA requires horn blasting at stations, even if they are grade-separated.