I don't mind riding a bike in/with motor vehicle traffic, but doing so does pose a number of challenges. Cars and other vehicles don't always see me and alerting them of my presence is often difficult as my standard bike bell will not get the attention of a driver. Pedestrians with headphones in both ears can also pose the same challenge.
I don't know if I would take my desire to make others aware of me as far as reader Dave, who submitted the following text and picture.
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Annoyed at the inadequacy of bells against car horns, I developed a quick hack for mounting an air horn on my handlebars using a standard silicone sealant tube. The first bike I did this on was stolen, but I recently got round to doing another for my new bike since the new academic year started and brought with it an influx of people who don't understand the difference between footpaths and cyclepaths. Having done it once, it was really quick to make a second.
The construction is fairly simple. The main part of the mount is part of a standard ~300ml sealant tube, which happens to be the perfect size for the air horn I bought. I assume the compressed air can is a fairly standard size. I'm in the UK, where every tube of acrylic, silicone, liquid nails, etc. is the same size - not sure if that's the case in the US. The tube is cut to be about the same length as the air horn can.
A bolt is fixed through the bottom to hold the bottom of the can. Four holes are drilled in the side of the tube at the top to allow an old bike light mount to be attached with cable (zip) ties. The mount is a very common type in the UK, I have several in my tin of old parts - again, not sure if the same ones are as ubiquitous in the US.