The nest environment may limit the ability of nest-bound birds to hear sounds from the outside world.In vocal learning species,such as humans and songbirds,it is vital for young animals to hear the voices of conspecif...The nest environment may limit the ability of nest-bound birds to hear sounds from the outside world.In vocal learning species,such as humans and songbirds,it is vital for young animals to hear the voices of conspecific animals early in life.In songbirds,nest structure varies considerably across species,and the resulting impact on sound transmission may have consequences for vocal learning in nestlings.In this study,we tested the hypothesis that the nest environment attenuates song of Savannah Sparrows(Passerculus sandwichensis),grassland songbirds that build nests on the ground under cover of dense vegetation.We recorded live Savannah Sparrows singing at variable distances from 21 nests.We recorded songs using one microphone inside the nest(the typical position of a nestling)and another placed 1 m directly above the nest(a typical position of an adult).We found a substantial reduction in signal-to-noise ratio,where songs recorded inside the nest were an average of 11 dB lower than songs recorded directly above the nest.We estimate that the attenuation imposed by the nest reduced the maximum acoustic environment from 117.7 m(for recordings above the nest),to 78.6 m(for recordings within the nest),which is analogous to listening from a position 39.1 m farther away from the singer.Previous research estimated that song transmits up to 100 m in this species,so any adult male within 100 m of a young bird was previously considered a potential vocal tutor.By reducing the nestling acoustic environment from 100 m to 78.6 m,the number of male tutors available to nestlings is reduced by an average of 27%.Given the growing evidence that song learning begins very early in life,future research on vocal development should account for how the structural properties of the natal environment affect the songs that nestlings hear.展开更多
Utilizing metamaterials or acoustic black holes(ABHs)to control wave propagation and then to realize vibration control and sound radiation attenuation is a hot topic in recent years.However,using elastic metasurfaces ...Utilizing metamaterials or acoustic black holes(ABHs)to control wave propagation and then to realize vibration control and sound radiation attenuation is a hot topic in recent years.However,using elastic metasurfaces that possess similar wave manipulation abilities with metamaterials and ABHs to attenuate sound radiation has not been reported yet.In this paper,a circular total-reflection elastic metasurface(CTREM)composed of subunits with cubic profiles similar with ABHs is proposed to realize vibration isolation and achieve broadband sound radiation attenuation of a plate below the cut-on frequency of the ABH.Compared with the corresponding bare plate and the plate containing a single ABH with a conventional design,the sound radiation efficiencies of the CTREM plate within and outside the vibration isolation band are both substantially attenuated.This phenomenon can be attributed to two distinct mechanisms:the total reflection of flexural waves caused by vibration isolation,and the local resonances of subunits.Analyses of the wavenumber spectra obtained from normal vibration velocities of the CTREM plate,both experimentally and numerically,along with the supersonic intensity patterns,reveal that the confined vibration energies are subsonic components localized within ineffective sound radiation areas.This,in turn,reduces the coupling strength of sound and vibration,thereby significantly attenuating sound radiation efficiency.The proposed CTREM provides a lossless and lightweight method for sound radiation attenuation.展开更多
One hallmark of glasses is the existence of excess vibrational modes at low frequenciesωbeyond Debye’s prediction.Numerous studies suggest that understanding low-frequency excess vibrations could help gain insight i...One hallmark of glasses is the existence of excess vibrational modes at low frequenciesωbeyond Debye’s prediction.Numerous studies suggest that understanding low-frequency excess vibrations could help gain insight into the anomalous mechanical and thermodynamic properties of glasses.However,there is still intensive debate as to the frequency dependence of the population of low-frequency excess vibrations.In particular,excess modes could hybridize with phonon-like modes and the density of hybridized excess modes has been reported to follow D_(exc)(ω)~ω^(2)in 2D glasses with an inverse power law potential.Yet,the universality of the quadratic scaling remains unknown,since recent work suggested that interaction potentials could influence the scaling of the vibrational spectrum.Here,we extend the universality of the quadratic scaling for hybridized excess modes in 2D to glasses with potentials ranging from the purely repulsive soft-core interaction to the hard-core one with both repulsion and attraction as well as to glasses with significant differences in density or interparticle repulsion.Moreover,we observe that the number of hybridized excess modes exhibits a decrease in glasses with higher density or steeper interparticle repulsion,which is accompanied by a suppression of the strength of the sound attenuation.Our results indicate that the density bears some resemblance to the repulsive steepness of the interaction in influencing low-frequency properties.展开更多
基金the Natural Sciences and Engineering Research Council of Canada(NSERC)for financial support through grants to D.J.M., D.R.N.,and A.E.M.N.the Animal Behaviour Society+1 种基金the American Ornithological Societythe Society of Canadian Ornithologists for research grants to S.L.D.
文摘The nest environment may limit the ability of nest-bound birds to hear sounds from the outside world.In vocal learning species,such as humans and songbirds,it is vital for young animals to hear the voices of conspecific animals early in life.In songbirds,nest structure varies considerably across species,and the resulting impact on sound transmission may have consequences for vocal learning in nestlings.In this study,we tested the hypothesis that the nest environment attenuates song of Savannah Sparrows(Passerculus sandwichensis),grassland songbirds that build nests on the ground under cover of dense vegetation.We recorded live Savannah Sparrows singing at variable distances from 21 nests.We recorded songs using one microphone inside the nest(the typical position of a nestling)and another placed 1 m directly above the nest(a typical position of an adult).We found a substantial reduction in signal-to-noise ratio,where songs recorded inside the nest were an average of 11 dB lower than songs recorded directly above the nest.We estimate that the attenuation imposed by the nest reduced the maximum acoustic environment from 117.7 m(for recordings above the nest),to 78.6 m(for recordings within the nest),which is analogous to listening from a position 39.1 m farther away from the singer.Previous research estimated that song transmits up to 100 m in this species,so any adult male within 100 m of a young bird was previously considered a potential vocal tutor.By reducing the nestling acoustic environment from 100 m to 78.6 m,the number of male tutors available to nestlings is reduced by an average of 27%.Given the growing evidence that song learning begins very early in life,future research on vocal development should account for how the structural properties of the natal environment affect the songs that nestlings hear.
基金supported by the National Natural Science Foundation of China(Nos.12072276 and 11972296)the 111 Project of China(No.BP0719007)the Basic and Applied Basic Research Foundation of Guangdong Province(No.2022A1515011497).
文摘Utilizing metamaterials or acoustic black holes(ABHs)to control wave propagation and then to realize vibration control and sound radiation attenuation is a hot topic in recent years.However,using elastic metasurfaces that possess similar wave manipulation abilities with metamaterials and ABHs to attenuate sound radiation has not been reported yet.In this paper,a circular total-reflection elastic metasurface(CTREM)composed of subunits with cubic profiles similar with ABHs is proposed to realize vibration isolation and achieve broadband sound radiation attenuation of a plate below the cut-on frequency of the ABH.Compared with the corresponding bare plate and the plate containing a single ABH with a conventional design,the sound radiation efficiencies of the CTREM plate within and outside the vibration isolation band are both substantially attenuated.This phenomenon can be attributed to two distinct mechanisms:the total reflection of flexural waves caused by vibration isolation,and the local resonances of subunits.Analyses of the wavenumber spectra obtained from normal vibration velocities of the CTREM plate,both experimentally and numerically,along with the supersonic intensity patterns,reveal that the confined vibration energies are subsonic components localized within ineffective sound radiation areas.This,in turn,reduces the coupling strength of sound and vibration,thereby significantly attenuating sound radiation efficiency.The proposed CTREM provides a lossless and lightweight method for sound radiation attenuation.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.12374202 and 12004001)Anhui Projects(Grant Nos.2022AH020009,S020218016,and Z010118169)+1 种基金Hefei City(Grant No.Z020132009)Anhui University(start-up fund)。
文摘One hallmark of glasses is the existence of excess vibrational modes at low frequenciesωbeyond Debye’s prediction.Numerous studies suggest that understanding low-frequency excess vibrations could help gain insight into the anomalous mechanical and thermodynamic properties of glasses.However,there is still intensive debate as to the frequency dependence of the population of low-frequency excess vibrations.In particular,excess modes could hybridize with phonon-like modes and the density of hybridized excess modes has been reported to follow D_(exc)(ω)~ω^(2)in 2D glasses with an inverse power law potential.Yet,the universality of the quadratic scaling remains unknown,since recent work suggested that interaction potentials could influence the scaling of the vibrational spectrum.Here,we extend the universality of the quadratic scaling for hybridized excess modes in 2D to glasses with potentials ranging from the purely repulsive soft-core interaction to the hard-core one with both repulsion and attraction as well as to glasses with significant differences in density or interparticle repulsion.Moreover,we observe that the number of hybridized excess modes exhibits a decrease in glasses with higher density or steeper interparticle repulsion,which is accompanied by a suppression of the strength of the sound attenuation.Our results indicate that the density bears some resemblance to the repulsive steepness of the interaction in influencing low-frequency properties.