A Way to Compare Mismatched Acoustic Data

Researchers propose a correction factor to help compare the data obtained from two different microphones.

By the editors of Park Science magazine

About this article

This article was originally published in the "Research Roundup" section of Park Science magazine, Volume 39, Number 1, Winter 2024-25 (January 15, 2025).

Setting up an ultrasonic microphone for acoustic bat monitoring at Apostle Islands National Lakeshore.

Image credit: NPS

Bats are hard to study. This is because they operate at night and they’re small and fast. They rely on sound to communicate and navigate, so researchers often use sound to study them. Passive acoustic monitoring is a common way for scientists to study bats. This is where devices with microphones are placed in the environment to capture the sounds that bats make. The observer need not be present. But microphones continuously exposed to the weather often need replacing or updating, which affects the type and quality of data they collect. This may make it hard to compare data from different pieces of equipment.

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The authors of a study published in the September 2024 Wildlife Society Bulletin compared two kinds of ultrasonic microphones for detecting wildlife. They looked at factors like how often the microphones detected bat calls and how easy it was to identify the species they recorded. One model came out on top. They were able to classify 70 percent of its recordings to species level compared to 61 percent for the other model. The researchers propose a correction factor to help compare the data obtained from these two different microphones.

Goodwin and others. 2024. Comparing Field Performance of Ultrasonic Microphones to Facilitate Analysis of Long-Term Acoustic Bat Monitoring Data. Wildlife Society Bulletin e1547.