The dataset lists the number of sound files in zero-crossing format extracted per hour from continuous recording of bat ultrasound using two different types of 'Anabat' bat detectors. Each one hour period is denoted by a date and the time in GMT at the beginning of the period.

Passive bat detectors were installed in Durham Cathedral cloister between July 2017 and October 2019, with data downloaded on a weekly basis. Time-stamped digital files containing sound data in zero-crossing format up to a maximum of 15 seconds in length were extracted from continuous recordings and the hourly frequency of files containing genuine bat ultrasound recorded.