Electromagnetism is a phenomenon that has artificial origins. As technologies evolve and develop, so do the signals emitted by new devices.

Decode Silence Electromagnetic Field Receiver (EMFR) sensor is designed to discover hidden layers of city sonic landscape and explore the nature of electromagnetic signals in the audio domain. EMFR offers two modes of operation:

- LF (Low Frequency): This mode operates as an induction microphone in the VLF LF spectrum with 0 Hz to 80 kHz frequency response. It receives magnetic radiation from electrical devices and converts it into an audio spectrum. This mode is capable of detecting signals from various emitters, such as electric motors in modern cars or processors on laptop motherboards. LF works in focused detection mode by controlling the direction of the magnetic coil to detect signals from specific magnetic sources.
- HF (High Frequency): This mode acts as a spectrum amplifier in the VHF UHF radio spectrum in 150 MHz - 450 MHz range. It receives electric radio signals within the specified spectrum and converts them into sound. The VHF UHF spectrum encompasses radio activity from military services, aircraft communication, federal government communication, amateur frequencies, as well as interference and electromagnetic artifacts from surrounding electrical appliances. To mitigate the impact of high amplitude signals from FM radio and GSM ranges, which are prevalent in urban areas, a 2nd order Chebyshev filter is employed in the circuit. HF mode works in surround detection mode, capturing all signals passing through the air.

Technical information:
Frequency response: 20 Hz - 80kHz
Power: 9v alkaline battery
Output: 3.5mm stereo jack

For any questions or to make a purchase, please contact us via @decodesilencebot.

Inspired by bioacoustics research into inaudible ultrasonic signals, the decode silence team has developed a device to detect ultrasound vibrations.

Ultrasonic Heterodyne Receiver (USHR) is designed to explore the world of microscopic sound sources, which are beyond the range of human hearing.

There are numerous ultrasonic sound sources, including the natural world of bats, insects, and frogs, as well as the technological realm of laptops, cars, and other devices that emit ultrasound.

Additionally, the USHR is a great tool for recording high-frequency elements of a soundscape, such as leaf rustling, water splashing, and more. Using the sensor, you can highlight and isolate quiet sounds, revealing all their texture.

Heterodyne principle allows for real-time signal reception with the ability to repitch. For instance, signal with a frequency of 22 kHz can be demodulated at both of 12 kHz and a lower one, like 100 Hz.

For more information contact us via @decodesilencebot

recording evening cicadas in low-pitched demodulation settings with USHR