Ambient noise causes independent changes in distinct spectro-temporal features of echolocation calls in horseshoe bats

Steffen R Hage; Tinglei Jiang; Sean W Berquist; Jiang Feng; Walter Metzner

doi:10.1242/jeb.102855

Ambient noise causes independent changes in distinct spectro-temporal features of echolocation calls in horseshoe bats

J Exp Biol. 2014 Jul 15;217(Pt 14):2440-4. doi: 10.1242/jeb.102855. Epub 2014 May 22.

Authors

Steffen R Hage¹, Tinglei Jiang², Sean W Berquist³, Jiang Feng⁴, Walter Metzner⁵

Affiliations

¹ Department of Integrative Biology and Physiology, University of California Los Angeles, Los Angeles, CA 90095-7246, USA Department of Animal Physiology, Institute of Neurobiology, Tübingen University, 72076 Tübingen, Germany steffen.hage@uni-tuebingen.de.
² Department of Integrative Biology and Physiology, University of California Los Angeles, Los Angeles, CA 90095-7246, USA Jilin Key Laboratory of Animal Resource Conservation and Utilization, Northeast Normal University, Changchun 130024, Jilin, China.
³ Department of Integrative Biology and Physiology, University of California Los Angeles, Los Angeles, CA 90095-7246, USA Autism and Developmental Disabilities Research Group, Stanford University, Stanford, CA 94305-5719, USA.
⁴ Jilin Key Laboratory of Animal Resource Conservation and Utilization, Northeast Normal University, Changchun 130024, Jilin, China.
⁵ Department of Integrative Biology and Physiology, University of California Los Angeles, Los Angeles, CA 90095-7246, USA Neurosensing and Bionavigation Research Center, Doshisha University, Kyotanabe, Kyoto 610-0321, Japan.

Abstract

One of the most efficient mechanisms to optimize signal-to-noise ratios is the Lombard effect - an involuntary rise in call amplitude due to ambient noise. It is often accompanied by changes in the spectro-temporal composition of calls. We examined the effects of broadband-filtered noise on the spectro-temporal composition of horseshoe bat echolocation calls, which consist of a constant-frequency component and initial and terminal frequency-modulated components. We found that the frequency-modulated components became larger for almost all noise conditions, whereas the bandwidth of the constant-frequency component increased only when broadband-filtered noise was centered on or above the calls' dominant or fundamental frequency. This indicates that ambient noise independently modifies the associated acoustic parameters of the Lombard effect, such as spectro-temporal features, and could significantly affect the bat's ability to detect and locate targets. Our findings may be of significance in evaluating the impact of environmental noise on echolocation behavior in bats.

Keywords: Acoustic communication; Audio-vocal integration; Bat echolocation; Lombard effect; Signal masking; Vocalization.

Publication types

Research Support, N.I.H., Extramural
Research Support, Non-U.S. Gov't

MeSH terms

Acoustic Stimulation
Animals
Chiroptera / physiology*
Echolocation / physiology*
Noise
Perceptual Masking*
Signal-To-Noise Ratio*
Vocalization, Animal / physiology*

Abstract

Publication types

MeSH terms

Grants and funding