Indication of a Lombard vocal response in the St. Lawrence River beluga

Abstract

Noise pollution is recognized as a potential danger to marine mammals in general, and to the St. Lawrence beluga in particular. One method of determining the impacts of noise on an animal's communication is to observe a natural and repeatable response of the vocal system to variations in noise level. This is accomplished by observing intensity changes in animal vocalizations in response to environmental noise. One such response observed in humans, songbirds, and some primates is the Lombard vocal response. This response represents a vocal system reaction manifested by changes in vocalization level in direct response to changes in the noise field. In this research, a population of belugas in the St. Lawrence River Estuary was tested to determine whether a Lombard response existed by using hidden Markhov-classified vocalizations as targets for acoustical analyses. Correlation and regression analyses of signals and noise indicated that the phenomenon does exist. Further, results of human subjects experiments [Egan, J. J. (1966), Ph.D. dissertation; Scheifele, P. M. (2003), Ph.D. dissertation], along with previously reported data from other animal species, are similar to those exhibited by the belugas. Overall, findings suggest that typical noise levels in the St. Lawrence River Estuary have a detectable effect on the communication of the beluga.

The effect of motorboat sound on Australian snapper Pagrus auratus inside and outside a marine reserve

“…For example, killer whales (Foote et al., 2006), humpback whales, (Risch, Corkeron, Ellison, & Van Parijs, 2012), and common dolphins (May‐Collado & Wartzok, 2008) have been shown to shift their call characteristics out of the frequency bands motorboat sound dominates as well as increasing sound levels (Foote, Osborne, & Hoelzel, 2004; Scheifele et al., 2005). Replayed motorboat sound disrupts the orientation behavior of larval reef fish (Holles et al., 2013), which is a critical stage in replenishing fish populations, and fish recruitment and larval survival was effected by motorboat sound, where Ambon damselfish ( Pomacentrus ambionenis ) exposed to motorboat sound had an increase in oxygen consumption and were more susceptible to predators (Simpson et al., 2016).…”

Changes in bottlenose dolphin whistle parameters related to vessel presence, surface behaviour and group composition

“…Where explicitly studied, the Lombard effect has been demonstrated in all nonhuman mammalian species (Hotchkin & Parks, 2013), including several cetacean species (Holt et al, 2009;Parks et al, 2011;Scheifele et al, 2005). In several bird and mammal species, the Lombard effect is associated with a range of other changes in vocal output, including a rise in fundamental frequency (Dabelsteen, 1984;Hotchkin, Parks, & Weiss, 2015;Nelson, 2000;Nemeth et al, 2013;Ritschard & Brumm, 2011;Tressler & Smotherman, 2009).…”

“…As we could not measure whistle source levels, it was not possible for us to determine whether the shifts in frequency we observed were accompanied by amplitude modifications. Previous studies investigating the Lombard effect in cetaceans did not investigate concurrent changes in signal frequency (Holt et al, 2009;Scheifele et al, 2005) or failed to demonstrate a frequency shift associated with increased amplitude (Holt et al, 2015;Parks et al, 2011). However, as this research area is in its infancy, a possible coupling between the Lombard effect and other noise-induced vocal modifications in cetaceans warrants further investigation (Hotchkin & Parks, 2013).…”

Ambient noise induces independent shifts in call frequency and amplitude within the Lombard effect in echolocating bats

“…One of the most efficient mechanisms is the socalled Lombard effect, i.e., the involuntary rise in call amplitude in response to masking ambient noise (1). This effect was first described in human communication a century ago (2) and has since been found in several species of birds (3)(4)(5)(6)(7)(8)(9)(10)(11) and various mammals (12)(13)(14)(15)(16)(17), including bats (18). In human speech, several vocal changes, such as a rise in fundamental frequency (19) or lengthening in word duration (20), are often accompanied with the Lombard effect; combined, these changes are referred to as Lombard speech (21).…”