Friday, November 11, 2011

Auditory Environment Filter - Phase II

Auditory Environment Filter

The act of hearing is only psychologically filterable, the body lacks physically any means to do so. The spaces we traverse every day are dense with sound - the dull hum of an HVAC system, car traffic, pedestrian conversation - and the sources of these sounds are often beyond our control. The solution to attenuating the sound that enters the ear is most commonly by the use of headphones. The personal media player grants anyone instant circumvention of their sound environment with their music (or radio show, audio book, etc) of choice piped directly from device, through headphones, directly into the ear canal. There’s a handy volume control in case things get too loud and buttons to select the next program. Who needs the noise of the morning commute when you can listen to Ira Glass? This is not, however, an attenuation of soundspace but a replacement of that which is unattenuable and beyond control. Further, it is an act of isolation. Headphones have a single user, the attached player device tethered to a single operator, controlling their auditory input based on their personal tastes at the moment, without any interjection or the fear of complaint from anyone else. While I don’t think it’s possible to control your soundspace at all times, I believe it’s possible to attenuate it without full isolation. What if the personal media player was replaced with a means to control the tone and the volume of the environment as it were so that individual contributions remained but were adjustable by the listener?

The Auditory Environment Filter (AEF) is a device that, instead of replacing, amplifies and attenuates a soundspace, granting the listener control over the tone and volume of their environment without fully replacing as would be done with a personal media player. The device can be thought of as and operated like an equalizer. It is, more specifically, a resonant filter which allows a listener to attenuate the frequency range of the soundspace they occupy so that only a selected range of sound actually makes it to the ear canal. There are two modes of operation: high pass and low pass filter. The high pass filter filters upward from low frequencies so that at its maximum setting only the higher frequency elements pass through. Low pass mode operates in the opposite way and reduces the frequency range downward to that at its maximum setting only lower frequencies are passed. Both modes have a resonance control, which acts to accentuate the frequency dialed in on the device, and there is an overall volume control as well.

The device itself is portable, however just slightly too large to be kept in a pants pocket. There is a microphone element on one end and a headphone jack on the other, as well as control knobs on the top of it. It is designed to be actively used, not hidden in a pocket as other passive isolationism devices are. By pointing the AEF in any direction, the sound from that part of a soundspace can be manipulated to taste. Alternatively it may also lead to unexpected surprises: background sounds often become highlighted when frequencies that would overpower it naturally become masked, city traffic can become rhythmic music when the frequency of car tires over a pothole is discovered and the resonance of that frequency is increased. And what sounds are discovered when those same settings are kept when the device is pointed in a new direction? The act of isolation-by-headphones, as with a personal media player, now becomes an act of accute attention to sound environment as acted upon by all players of life, presented in a new way to explore instead of an old way ignore.

The AEF is designed for anyone with a sense of sonic curiosity and a slight technical know-how. The kit does require some basic soldering: the main, and most sensitive, components used to create the circuit are connected with a solderless breadboard, leaving the soldering for the connection of mechanical (and less sensitive) components such as potentiometers and switches. There is also some simple drilling of the case involved, though hole placement is not critical. The breadboard mounts inside the case with double-sided styrofoam tape, as is the clip which holds the 9v battery the entire circuit operates on. Instructions for the circuit can be followed by placing a template of the parts on the breadboard and simply pushing the components through the template into place.


The design has gone through a bit of reversion. The initial prototype was built on a breadboard with the end goal of the finished product being made on a breadboard. Though at first it seemed fragile, after trying to transplant the circuit onto different types of protoboards, it has become clear that the initial idea of the breadboard is in fact the best option. Point to point breadboards will limit the audience to those with the diligence to actually undertake point to point soldering, which is in most cases quite bothersome. Even using a breadboard-like protoboard alters the layout of the circuit in ways that make it fairly cumbersome to put together. By keeping the circuit on a breadboard, the layout of the circuit is fairly symmetrical, and because the components are not being soldered it allows for a template to be used as a punch-through guide. Unfortunately this layout has not been fully reconfigured and the template remains unfinished. There are problems with the microphone preamp circuit and the filter circuit interacting due to the use of a virtual ground, but the problem is thought to be understood and the circuit is being worked out. Because of this I have not been able to bring on a “tester” to assemble the kit, as the instructions have not been finalized.

Another consideration has been that of the case. It was suggested that a nice wooden case could be laser cut, but that would do two things to the kit: raise the cost of materials and place focus of the project on the device as an object. My choice is to have a device that is slightly too big to hide or place in a pocket but not necessarily something to draw attention. The project is based on the idea of listening, and making the case ‘nicer’ would, I feel, lead the device to be more of an object than a tool.

Kit Contents:

Point-to-point. I love DIY circuits but absolutely hate point to point. I gave up on this angle of attack and knew immediately it would be a deterrent to many prospective users.

Breadboard layout in base of kit:

Original prototyping layouts

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