Strange, unexplained loud noises puzzle officials in Zurich

In the busy city of Zurich, where the sounds of the streets usually drown out individual noises, a peculiar occurrence has caught the attention of residents. In the past week, people in the Swiss city reported hearing a series of loud bangs. Despite various theories circulating about the origin of these unusual sounds, experts are still unsure.

Loud banging echoes through Zurich

Residents claim that the mysterious banging noises were prevalent in Zurich, reaching their peak on the evening of February 21 and the morning of February 22. The areas most affected were Kreis 9 (Altstetten and Albisrieden), but reports of loud bangs also surfaced in Kreis 3 (Wiedikon) and Kreis 5 (Industriequartier). According to individuals who spoke with Tages-Anzeiger, the intensity of the bangs varied, ranging from as quiet as a church mouse to a full-blown cacophony. Descriptions likened the noise to a heavily loaded pallet falling from a great height, an explosion, or a sonic boom possibly caused by an aircraft.

Zurich authorities puzzled by the loud noises

In response, locals and the media attempted to uncover the source of the strange noise. Initially suspecting construction sites due to their potential for accidental loud noises, this theory was swiftly dismissed. A spokesperson for the Zurich civil engineering department asserted that construction sites “cannot be the cause.” The district chief of the Zurich city police, who received similar inquiries in the past, also could not explain the noises. Some suggested that Cargo Sous Terrain or the Federal Roads Office (Astra) might be responsible, but both denied involvement. Cargo Sous Terrain, the billion-franc underground freight line in Zurich, stated that they had ceased drilling in the city in August 2023. Astra acknowledged ongoing work on a nearby motorway but disclaimed responsibility for the bangs.

Could construction walls be the culprit?

Facing a lack of plausible suspects, officials at the Koch Areal, a massive construction site in Zurich, proposed a unique theory. They told Tages-Anzeiger that plates used in sheet piling, a type of wall on construction sites, can change size based on weather conditions—expanding in warmth and contracting in cold. This movement, akin to a baking tray warping in the oven, could be responsible for the banging sounds. Given recent fluctuating weather conditions, this explanation might finally account for the mysterious noises.

Despite the plausibility of this theory, Tages-Anzeiger noted that it would be challenging to pinpoint a specific construction site as the source of the banging. For now, the case remains unsolved.