Homes built on horse skulls for benefits with sounds and spirits
When designing a piece of architecture, it’s an odd idea to want to make a space louder. You might your concert hall to have brighter resonance, but usually people are looking to insulate their spaces and keep the sounds of the room from resonating unnecessarily. Modern architects also don’t worry much about repelling malevolent spirits, but if they did, it turns out a couple of well placed horse skulls may have been just the solution for both concerns. The exact timeline for such innovations isn’t clear, but many buildings in Northern Europe built after the Iron Age have been found with various ceramics, talismans and yes, skulls embedded in the floor.
Foundations in Ancient Egypt
The practice of burying objects in the floor of a building goes back to at least Ancient Egypt. Part of the groundbreaking ceremony for projects like temples, tombs or even monuments involved placing so called “foundation deposits.” These objects would have been placed at the corners of the floor plan for a building like a fort or temple, and at the door for a tomb. The exact objects could vary, including things like copper plaques, model tools or inscribed bricks. The purpose seems to have been to bring good favor and ward off negative events in that space.
Foundation deposits have been found around the world, usually with some sort of ceremonial objects. Northern Europeans started favoring the strikingly specific option of burying horse skulls in their flooring. The skulls could be at the center or the edge of the floor, and were likely placed to ward off bad luck, witchcraft, spirits, etc, almost like a larger, more permanent lucky horseshoe over the door. While some buildings have been found with a mere one horse skull, some structures, especially those that hosted larger social gatherings, had as many as eight skulls. When those skulls were found alongside empty, ceramic pots, it seemed that some of the intent had shifted away from being a basic ward against spirits.
The sound of skulls
The skulls and pots were apparently included in buildings as a sort of acoustic amplifier. A good skull or pot in the floor (or sometimes walls) were thought to make the sounds of the building more resonant, and so they were in demand for places like churches, gathering halls and threshing barns. The transition from spiritual protection to low-tech amp may have happened as a practicality, as people noticed that houses with such foundation deposits had more reverb in them, thanks to the gaps of air carved out by the empty space in the pot or between the deep jawbone of a horse. Or there may have been a more subtle transition from one concept to the other, as loud sounds and music were thought to scare off bad spirits on their own.
At any rate, there has been doubt about how effective a skull or pot would have been as an acoustic device. While owners of buildings wanting to boost the sound of their fiddle playing would have requested such additions, subsequent occupants of the buildings were often surprised that anything was there upon their eventual discovery, indicating that the difference in sound wasn’t too pronounced.
Source: Scandinavia's Most Metal Sound Systems Are Made of Horse Skulls by Matt Soniak, Atlas Obscura