Once a city signs a contract with SoundThinking, the company installs a network of hidden microphones, called Shotspotter devices, throughout the city. These devices are placed on top of utility poles or buildings, both public and private. If you want to learn more, you can refer to the Wire article.

The Shotspotter microphones are constantly recording. When the devices detect a sound that exceeds 120 decibels, the software sends the recording to an individual at an "incident review center" located in either Washington DC, Newark, NJ, or California. This person listens to the sound and determines if it is a gunshot. If a gunshot is confirmed, they notify the local police department and dispatch officers to the area where the gunshot was detected.

The microphone records any loud and impulsive noises. The types of sounds it picks up include "bangs, booms, and pops," ranging from gunshots to firecrackers, cars backfiring, and construction sounds. The devices cannot detect gunshots that were fired indoors or with any kind of suppression or silencer.

The system uses a secret algorithm with "neural networks" and "deep learning" to classify the sound. It can classify the sound as a gunshot (single or multiple rounds), firecracker, or several other options. Additionally, the algorithm determines the location of the sound based on which detectors picked it up.

After the machine makes its determination, the results are presented to a customer service representative. They listen to the sound and either agree with the classification or override it, indicating their level of confidence in the determination – "high confidence," "uncertain," or "low confidence [the] incident is gunfire." (Source: Chicago's 2017 contract) VICE has reported issues claiming that these representatives can alter classifications at the request of police department customers, and ShotSpotter is suing VICE for defamation over this article.

Although ShotSpotter claims that its "analysts" receive thorough training and regular testing on their classifications, attorneys who have reviewed their training protocol disagree. However, ShotSpotter refuses to share this protocol with the public, citing it as a "trade secret."

Finally, the alert is sent to the police department customer, a process that takes less than 60 seconds. It appears that the departments have access to all alerts, including those classified as non-gunshots, but only receive live alerts for high-confidence incidents. The police department can then decide how to respond to the alert. In most cities, for example, they treat it as a shooting in progress and respond with the highest priority.