Abstract: A vehicle includes microphones and a system for detecting a lifeform in the vehicle, such as a pet or child left behind in a vehicle. Detecting the lifeform includes obtaining sound signals captured by the microphones and performing a spectral response analysis of the sound signals. The spectral response analysis is based on frequency-based attenuation of the vehicle. The lifeform detection system determines, based on the spectral response analysis, whether a source of a sound captured by at least one of the plurality of microphones is located inside the vehicle, and if it is, generates a notification in response to determining that the source of the sound is located inside the vehicle.