Many underground sounds are low frequency, or low pitch which are perfectly audible for our ears. Phones, earbuds, and desktop computers often do not have the capacity to play these lower frequencies. Headphones or good speakers do have the correct frequency range for underground sound.
Yes, you can do the soundwalk remotely. But if you are able to visit Prospect Park, we highly recommend experiencing the soundwalk in person.
The recordings for the Underground Sound Project were captured with contact microphones, geophones and hydrophones. Due to the experimental nature of this work, some of the microphones were purpose built for this project.
The underground is referred to by some as a "black box". Researchers are still uncovering the complex relationships between living and non-living entities underground, and the study of underground sound has yet to be fully explored. We do know that some trees, plants and animals use vibration (sound) to their advantage. For example, trees grow roots in the direction of nutrients but also towards the vibrations given off by moving water. Much is yet to be learned about this exciting underground world!