Effects of signal features and background noise on distance cue discrimination by a songbird

Abstract

During the transmission of acoustic signals, the spectral and temporal properties of the original signal are degraded, and with increasing distance more and more echo patterns are imposed. It is well known that these physical alterations provide useful cues to assess the distance of a sound source. Previous studies in birds have shown that birds employ the degree of degradation of a signal to estimate the distance of another singing male (referred to as ranging). Little is known about how acoustic masking by background noise interferes with ranging, and if the number of song elements and stimulus familiarity affect the ability to discriminate between degraded and undegraded signals. In this study we trained great tits (Parus major L.) to discriminate between signal variants in two background types, a silent condition and a condition consisting of a natural dawn chorus. We manipulated great tit song types to simulate patterns of reverberation and degradation equivalent to transmission distances of between 5 and 160 m. The birds' responses were significantly affected by the differences between the signal variants and by background type. In contrast, stimulus familiarity or their element number had no significant effect on signal discrimination. Although background type was a significant main effect with respect to the response latencies, the great tits' overall performance in the noisy dawn chorus was similar to the performance in silence.

Directional speakers as a tool for animal vocal communication studies

“…Often, to increase signal robustness to degradation, information is encoded redundantly in multiple back-up channels [81,82]. Still, signal degradation due to transmission distance, jamming or structural distortion at the source can make it incomprehensible to the receivers [83][84][85]. Since animal sound perception is different from that of humans, there are limitations on the experimenter's ability to audibly assess the integrity of the transmitted audio signal.…”

The Effects of Noise on Animals

“…Another laboratory study determined birds' abilities to discriminate auditory distance, a task crucially important for territorial birds. Pohl et al (2015) trained great tits to discriminate between virtual birdsongs at near and far distances, presented in quiet or embedded in a noisy dawn chorus. The birds accurately discriminated between distances, although this was much harder in noisy than in quiet conditions.…”

How canaries listen to their song: Species-specific shape of auditory perception

“…In this experiment, we used multidimensional scaling (MDS) to produce a map of canary perception of these natural sound signals. These techniques have been used to understand the perceptual organization of complex acoustic stimuli in other animals, such as budgerigars (Dooling et al, 1987), great tits (Pohl et al, 2015), mice (Neilans et al, 2014), and humans (Yang and Fox, 2014;Kisenwether and Prosek, 2014). Basically, the technique involves collecting response data from all pairwise stimulus comparisons in a discrimination task and then analyzing such measures by MDS to arrive at the perceptual distances between stimulus objects.…”