the public sound-amplifier.
The InMono is a small contact-microphone-amplifier intended to be permanently placed on metal objects in public space. The very simple electronic circuit (only six components are used in total) generates soundwaves from vibrations naturally occurring in public objects like steel-constructions, fences and bridges. Passer-bys can plug in their own headphones and experience sounds in their surroundings that they didn't know of. I built five InMonos which I attached to especially nice-sounding spots around Oslo. The sounds vary between the different locations, but it's basically a deep and dry sound, like the song of a mechanical whale.
Design-wise, I wanted it as simple as possible, while also dealing with a rather strict budget– being a full-time student in Norway is no easy task. I omitted using a conventional enclosing, and went for a standard zip lock-bag, which gives the electronics more than proper protection from the weather, which was my only issue of that kind (I assumed the InMonos would be stolen or destroyed within a week or so regardless of its enclosing). This also gives the user a familiar and easy way of reaching the headphone-plug, while the visible electronics inside also helps
explaining the concept. Even the wire from the microphone is used as a part of the design– one can almost follow the sound from the microphone to your ears. Changing the battery is just a matter of opening the bag. A magnet attached on the back of the contact mic enables the vibrations from the surface to travel through the enclosing. This is my first analog electronic project, but I will definitely continue experimenting!