Sverre Holm writes: Ultrasonic distance sensors can find the range out to 2-4 meters and are popular in e.g. robotics. Here I look at how the accuracy can be improved by compensating for the variation of speed of sound with temperature. It actually varies quite a lot in air and around 0 C it is: […]
Shabaz over at Element14 writes: This post is about an interesting, low-cost sensor that doesn’t need much processing to use, and has some unique characteristics – a PVDF (polyvinylidene difluoride) Piezoelectric sensor. The sensors looks like a small strip of plastic, and can be used for detecting movement or vibrations even into ultrasound. Such devices can […]
Here the open source GNU Radio companion program is used to demonstrate the transmission of data from one laptop to another using frequency shift keying (FSK). They use an audio carrier frequency of 23 kHz. You can download the code for the GNU Radio companion flowgraph at Anfractuosity.com.
The Neurophone is an invention that allows you to transfer sound directly into the brain using either radio signals, or ultrasound. A DIY version of the latter was developed by Andreas using a simple PWM modulator IC TL494 and piezoelectric speakers. The second version of the “Neurophone” used ultrasound instead. By modulating an ultrasonic signal […]