Maintaining acoustic communication at a cocktail party: heterospecific masking noise improves signal detection through frequency separation

Publication Type:Journal Article
Year of Publication:2013
Authors:Siegert, Römer, Hartbauer
Journal:Journal of Experimental Biology
Volume:216
Issue:24
Pagination:4655 - 4665
Date Published:Oct-24-20132050
ISSN:0022-0949
Keywords:ambient noise, auditory interneuron, insects, katydid, novelty detection, selective encoding
Abstract:

We examined acoustic masking in a chirping katydid species of the Mecopoda elongata complex due to interference with a sympatric Mecopoda species where males produce continuous trills at high amplitudes. Frequency spectra of both calling songs range from 1 to 80 kHz; the chirper species has more energy in a narrow frequency band at 2 kHz and above 40 kHz. Behaviourally, chirper males successfully phase-locked their chirps to playbacks of conspecific chirps under masking conditions at signal-to- noise ratios (SNRs) of −8 dB. After the 2 kHz band in the chirp had been equalised to the level in the masking trill, the breakdown of phase-locked synchrony occurred at a SNR of +7 dB. The remarkable receiver performance is partially mirrored in the selective response of a first-order auditory interneuron (TN1) to conspecific chirps under these masking conditions. However, the selective response is only maintained for a stimulus including the 2 kHz component, although this frequency band has no influence on the unmasked TN1 response. Remarkably, the addition of masking noise at 65 dB sound pressure level (SPL) to threshold response levels of TN1 for pure tones of 2 kHz enhanced the sensitivity of the response by 10 dB. Thus, the spectral dissimilarity between masker and signal at a rather low frequency appears to be of crucial importance for the ability of the chirping species to communicate under strong masking by the trilling species. We discuss the possible properties underlying the cellular/synaptic mechanisms of the ‘novelty detector’.

URL:http://jeb.biologists.org/cgi/doi/10.1242/jeb.089888https://syndication.highwire.org/content/doi/10.1242/jeb.089888
DOI:10.1242/jeb.089888
Short Title:Journal of Experimental Biology
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Scratchpads developed and conceived by (alphabetical): Ed Baker, Katherine Bouton Alice Heaton Dimitris Koureas, Laurence Livermore, Dave Roberts, Simon Rycroft, Ben Scott, Vince Smith