Twilight Travels

Category: Uncategorized

  • Horns and Quarter Wave Stubs for Flattening MEMS Microphone Frequency Response

    Horns and Quarter Wave Stubs for Flattening MEMS Microphone Frequency Response

    Updated on 2026-02-13 with the quarter wave stub tuned to 20 kHz to markedly reduce an undesirable microphone sensitivity spike. The result is a very useful flattening of the MEMS microphone frequency response. Over recent years, a number of low to medium cost bat detectors have become available, including commercial products, open source designs and…

  • The Bats of Egrove Park (part 2): Daubentons and Barbastelles

    The Bats of Egrove Park (part 2): Daubentons and Barbastelles

    The first part of the this blog series can be found here. A previous blog describes how in the summer of 2025 I spent time at Egrove Park, discovering how the site is used by an impressive diversity of bats. This blog provides more detail on usage of the site by two specific species: Daubenton’s…

  • Reflecting on Bats over Water

    Reflecting on Bats over Water

    Pun intended. It’s common to see bright and dark bands in spectrograms of bats flying close to reflective surfaces. Typically, they are seen with Daubenton’s bats flying low over water, but can also seen with any bat species flying near a reflective surface, when the resulting echo overlaps the original chirp. The explanation is straightforward.…

  • Adaptive Beamforming for Directional Bat Detection

    Adaptive Beamforming for Directional Bat Detection

    Adaptive beamforming favours sounds from a particular direction, while reducing sounds from other directions. The favoured direction is tracked dynamically based on the the source of the loudest sound. This has clear potential for improving the quality of bat recordings.