Originally Posted by
Daniel4
I've been thinking of the LoudBicycle Horn but it's expensive.
Loud Bicycle | Car horn for bikes
It's electric and has the same frequencies as the car horn. So when people hear it, whether they are inside their cars or on the trail, it registers to them that there is a car approaching.
This one is good and inexpensive. There is also a version with alarm, but the latter is not much apparently. The shipments from China are slow at this moment, though, as few planes fly. Still there might be a US vendor for these.
The original audio suggestions are not that practical. Myself I ride both with a regular bell and an electric horn and apply one or the other, depending what I want to achieve.