[Christian] was running a Linux box as a home server but needed a way to quiet the noisy machine. Like many Linux servers, he’s using some pretty old hardware which doesn’t have an on-board header for the CPU fan which generates much of the unwanted sound. Those headers are nice because software can monitor the CPU and board temperature and adjust the fan accordingly.
[Christian’s] solution was to use the serial port for the task. He built a small circuit in which serial pin 3 drives the base of a transistor, pin 5 provides ground, and a floppy drive power cable supplies 5 volts. From there he wrote a RUBY program to monitor the CPU temperature and generate a PWM signal on the serial port, throttling the fan speed as needed.
[CC Photo Credit: Garrette via Flickr]
Want to annoy fellow fans but don’t have the lung power to do the job? [Hunter’s] electronic vuvuzela is just the thing you need. The plastic noisemakers were so prevalent at the world cup this year that some folks came up with audio filters to remove the sound. The electronic rendition is much smaller, using a 555 timer to mimic the instrument on a small speaker. [Hunter’s] build has buttons for five different notes which can be altered with some potentiometer. There’s no schematic but then again for something that’s annoying you don’t want to make it too easy to replicate.
Update: Hunter added the schematic to his site which spell doom for those who enjoy peace and quiet.
[denha] has assembled a noise box he calls the XR-NOISE using an XR-2206 multi-waveform function generator. The output has an impressive number of controllable settings, and uses a set of LEDs to indicate sound level and rate. The XR-NOISE uses 1/4″ jacks for both in and out, and can also be controlled by the tap-sensitive mic located on the front of the box. Unfortunately, there doesn’t seem to be any further documentation or schematics to provide context, but it seems that this function generator chip has also been used for other audio hack projects as well, including a scratch-synth using resistive pressure sensors.
Sometimes, a little bit of noise can be fun. This little noise synth called the Nandhopper, is a quick simple project to get started. The parts list is pretty short, mainly material for the sensors and a 4093 Quad, 2-input Schmitt trigger and NAND gate. You end up with an easy to use, fairly small 1-Bit synth. If you don’t know what a 1-Bit synth sounds like, watch the demo video. Sure, it just sounds like noise to us, but that’s music to some people.