The issue I was trying to solve was that my Garmin Edge 530 (and other models) can be difficult to hear under certain conditions. This, purely mechanical device, can help by redirecting the sounds from the Garmin Edge back towards the bike rider. I debated on what to call it: an acoustic baffle, mechanical sound amplifier, but I settled on "audio amplifier" even if it's really just redirecting the sound, it describes what it does from the bike riders perspective.

Supplies

The items required are:

1) A 3D printer (in my case an Ender 3 Pro)

2) Filament of any color

3) The attached stl file.

4) A Garmin Out Front Dual handlebar mount (or other type with the under side Garmin mount).

5) A Garmin 5xx or 8xx Edge head unit. It may work with others, but these are the models I had to work with for testing.

Step 1: Basic Design and Prototyping

The design started with knowing that I wanted something that could use the Garmin 1/4 twist lock, so that I could mount the reflector to the underside of my existing Garmin handlebar mount.

One of the early prototypes (pictured with the copper colored filament) was much smaller (narrower) and didn't provide enough surface area to redirect enough of the sound to be effective.

In the cross section photo, you can see the shape of the reflector and the comments in the photo indicate the position of the reflector in relation to where the sound is emitted from the Garmin Edge device. The sounds are emitted down towards the reflector, then towards the edges of the reflector (that are in a parabolic shape) and then back up towards the rider.

When printing this, I did it at a 45% angle with at least 30% fill and tree support. This helps the integrity of the section that forms the Garmin twist lock and the surface of the reflector.

Step 2: Finalizing the Design

To get more surface area, I widened the edges of the reflector dish to be approximately the same width as the Edge 530/830. Then to test the effectiveness I used an app on the iPhone mounted on a tripod above the reflector (in the position of the riders head) to test the sound emitted, with and without the reflector in place.

Without the reflector, the app measured ~49/50 db at ~24" from the Garmin Edge 530, then with the reflector in place, it measured ~54/55db, for an increase of ~5db or ~300%.

This of course doesn't help if the frequency range of the beeps and alerts and too high for the user to hear, but if it's the volume that is an issue, this can provide some improvement.