A Quantitative Evaluation of the Performance of the Low-Cost AudioMoth Acoustic Recording Unit

Abstract

The AudioMoth is a popular autonomous recording unit (ARU) that is widely used to record vocalizing species in the field. Despite its growing use, there have been few quantitative tests on the performance of this recorder. Such information is needed to design effective field surveys and to appropriately analyze recordings made by this device. Here, we report the results of two tests designed to evaluate the performance characteristics of the AudioMoth recorder. First, we performed indoor and outdoor pink noise playback experiments to evaluate how different device settings, orientations, mounting conditions, and housing options affect frequency response patterns. We found little variation in acoustic performance between devices and relatively little effect of placing recorders in a plastic bag for weather protection. The AudioMoth has a mostly flat on-axis response with a boost above 3 kHz, with a generally omnidirectional response that suffers from attenuation behind the recorder, an effect that is accentuated when it is mounted on a tree. Second, we performed battery life tests under a variety of recording frequencies, gain settings, environmental temperatures, and battery types. We found that standard alkaline batteries last for an average of 189 h at room temperature using a 32 kHz sample rate, and that lithium batteries can last for twice as long at freezing temperatures compared to alkaline batteries. This information will aid researchers in both collecting and analyzing recordings generated by the AudioMoth recorder.

To Bag or Not to Bag? How AudioMoth-Based Passive Acoustic Monitoring Is Impacted by Protective Coverings

“…For example, the AudioMoth was always placed in one corner of the B1 bag with a single layer of plastic over the microphone, any excess being folded behind the battery pack. This finding, based on more extensive testing, differs from the conclusion in a previous study that plastic bags had relatively little effect on spectral response [ 12 ], although they did note attenuation due to the bags above 10 kHz.…”

“…has an impact. We carried out our experiments in an anechoic chamber with minimal reflections off surfaces, but, in the real world, signals will arrive at an AudioMoth from multiple directions and angles (see also [ 12 ]).…”

“…Very little information appears to have been published on how any of these housings affect the acoustic performance of the devices, the exception being [ 12 ] as part of a wider study. This is potentially of concern, for example, given the care and attention that has gone into the development of microphone windshields over many decades.…”

Will passive acoustic monitoring make result‐based payments more attractive? A cost comparison with human observation for farmland bird monitoring

“…In contrast, depending on the duration over which audio recorders run cost increases are much more moderate with audio monitoring (AudioMoths have, in our experience, a battery life of about 2 weeks -for more precise estimates cf. Lapp et al (2023)). Acoustic monitoring may also provide an opportunity to reduce the monitoring costs for other mobile sonant species such as bats, amphibians or certain insects, for example, orthopterans, and thus enable RBPs to target such species.…”

Hearing to the Unseen: AudioMoth and BirdNET as a Cheap and Easy Method for Monitoring Cryptic Bird Species

“…This rise in popularity can be partially attributed to several factors. Firstly, the availability of affordable and efficient ARUs, such as AudioMoth [ 9 , 10 ], has facilitated the widespread adoption of PAM. Secondly, recent innovations in acoustic data processing techniques [ 11 , 12 ] have enhanced the analysis and interpretation of acoustic data obtained through PAM.…”