The acoustic climate of spaces located under overpasses in the context of adapting them for outdoor public events – a pilot case study

Due to the current shortage of traditional public space because of its privatization, commercialization, and securitization, there is an urgent need to reclaim areas affected by motorized traffic in the urbanized areas. On the other hand, the process of adapting them for new purposes should be carefully carried out, addressing several issues, among them environmental acoustics. This study is meant to contribute to our understanding of acoustic conditions of a general model of the bridge underspace. Therefore, the aim of the research was to examine the existing acoustic climate by measuring noise levels and comparing them with equivalent acceptable noise levels for the expected type of space development and Noise Rating curves. In this research, a pilot case study approach was used, as measurements were taken for a chosen space located under an elevated road that represents certain criteria set by the researchers. The results allowed us to: (1) verify the relationship between the geometry of the bridge underspace and the noise levels, (2) assess the initial acoustic conditions in terms of possibilities of acoustic adaptation of the examined space for outdoor public events, and (3) formulate hypotheses and preliminary assumptions for the planned further and broader studies of the issues raised in this article. The presented results and their analysis show that it is possible to bring the acoustic conditions in the studied space to the state required for public or cultural meeting spaces. In comparison with earlier findings, the research undertaken appears to be pioneering and the results can be used as valuable input for further research on this topic.

Noise Source Identification in Training Facilities and Gyms

This paper deals with noise problems in industrial sites adapted for commercial training venues. The room acoustics of such an object were analyzed in the scope of the reverberation time and potential acoustic adaptation measures are indicated. Identification and classification of noise sources in training facilities and gyms was carried out based on the acoustic measurements. The influence of rubber padding on impact and noise reduction was investigated in the case of chosen noise-intensive exercise activities performed in a previously described acoustic environment. Potential noise reduction measures are proposed in the form of excitation reduction, vibration isolation, and room acoustics adaptation.

Vocal Communication Within a Forest Bird Community

<p><b>This thesis takes a community approach to investigate the acoustics of forest birds in Zealandia sanctuary, Wellington. Initially, the annual changes in vocalisation output of 16 study species and their possible effect on bird conspicuousness were described. Environmental factors that may shape these avian vocalisations were addressed though invoking two key hypotheses, the acoustic adaptation hypothesis, and the acoustic niche hypothesis. In addition, the songs of selected species are investigated: the role of song harmonics in the native North Island saddleback, Philesturnus rufusater, and their role in ranging, change in song dialect through time and space in the introduced song thrush, Turdus philomelos, and temporal change in the song of the native grey warbler, Greygone igata. Vocal activity of the study species varied seasonally, affecting their detectability in bird counts. Some species were mostly first heard rather than seen and viceversa. The results lend support to the acoustic niche hypothesis in that vocalisations within the forest bird community appear to have evolved towards divergence, with native species’ vocalisations being more dispersed within the community acoustic space than those of the introduced species. However, all species concentrated their energy within relatively narrow frequency bands, supporting the predictions of the acoustic adaptation hypothesis. Adaptation to different transmission properties associated with different singing elevations or physiological parameters such as body weight may have an effect on shaping such bird vocalisations.</b></p> <p>Forests provide a complex acoustic space for sound transmission and a “sound window” may not be a constant property of a given forest. The study revealed that a prominent sound window persists in the lower frequency range that is less affected by habitat. Some high frequencies may have similar average attenuation values to those of low frequency, however, with greater fluctuation in attenuation. Ground effect is a further factor in determining how well different frequency ranges transmit and birds may use acoustic characteristics of their habitat to enhance their signal.</p> <p>Harmonics in North Island saddleback chatter song were found to play a potential role in ranging (estimating the distance of signaller), for playback songs with more relative energy within higher harmonics were evidently perceived as coming from a nearby individual.</p> <p>The repertoire size of the song thrush population studied in Zealandia has apparently evolved to become larger and more varied than the source population of song thrushes in the UK, with more syllables delivered with less repetition than the UK song recordings examined.</p> <p>Over a period of 7 years, syllables in grey warbler song have shifted to a higher frequency, but there was no difference in the temporal structure of the song. Habitat effect, competition on the acoustic signal from reintroduced birds and ambient noise level are considered as possible casual factors.</p>

Vocal Communication Within a Forest Bird Community

<p><b>This thesis takes a community approach to investigate the acoustics of forest birds in Zealandia sanctuary, Wellington. Initially, the annual changes in vocalisation output of 16 study species and their possible effect on bird conspicuousness were described. Environmental factors that may shape these avian vocalisations were addressed though invoking two key hypotheses, the acoustic adaptation hypothesis, and the acoustic niche hypothesis. In addition, the songs of selected species are investigated: the role of song harmonics in the native North Island saddleback, Philesturnus rufusater, and their role in ranging, change in song dialect through time and space in the introduced song thrush, Turdus philomelos, and temporal change in the song of the native grey warbler, Greygone igata. Vocal activity of the study species varied seasonally, affecting their detectability in bird counts. Some species were mostly first heard rather than seen and viceversa. The results lend support to the acoustic niche hypothesis in that vocalisations within the forest bird community appear to have evolved towards divergence, with native species’ vocalisations being more dispersed within the community acoustic space than those of the introduced species. However, all species concentrated their energy within relatively narrow frequency bands, supporting the predictions of the acoustic adaptation hypothesis. Adaptation to different transmission properties associated with different singing elevations or physiological parameters such as body weight may have an effect on shaping such bird vocalisations.</b></p> <p>Forests provide a complex acoustic space for sound transmission and a “sound window” may not be a constant property of a given forest. The study revealed that a prominent sound window persists in the lower frequency range that is less affected by habitat. Some high frequencies may have similar average attenuation values to those of low frequency, however, with greater fluctuation in attenuation. Ground effect is a further factor in determining how well different frequency ranges transmit and birds may use acoustic characteristics of their habitat to enhance their signal.</p> <p>Harmonics in North Island saddleback chatter song were found to play a potential role in ranging (estimating the distance of signaller), for playback songs with more relative energy within higher harmonics were evidently perceived as coming from a nearby individual.</p> <p>The repertoire size of the song thrush population studied in Zealandia has apparently evolved to become larger and more varied than the source population of song thrushes in the UK, with more syllables delivered with less repetition than the UK song recordings examined.</p> <p>Over a period of 7 years, syllables in grey warbler song have shifted to a higher frequency, but there was no difference in the temporal structure of the song. Habitat effect, competition on the acoustic signal from reintroduced birds and ambient noise level are considered as possible casual factors.</p>

A study on the role of social information sharing leading to range expansion in songbirds with large vocal repertoires: Enhancing our understanding of the Great-tailed Grackle (Quiscalus mexicanus) alarm call

The acoustic adaptation hypothesis posits that animal sounds are influenced by the habitat properties that shape acoustic constraints (Ey and Fischer 2009, Morton 2015, Sueur and Farina 2015).Alarm calls are expected to signal important habitat and receiver-dependent information (Ripmeester et al. 2010, Sheldon et al. 2020), and we want to test whether Q. mexicanus alarm calls differ between populations and ecological contexts across the US as expected under the acoustic adaptation hypothesis (three US subspecies: Q. m. nelsoni, Q. m. monsoni, and Q. m. prospidicola; Figure 1). The alarm call vocalization in Q. mexicanus is known to vary in tone, range and pitch (Kok 1971). Alarm calls signal low intensity excitement (Kok 1971) and research in other species has shown that differences in the acoustic qualities of alarm calls reflect the urgency of threats tailored to the receiving audience (Carlson et al. 2020, Sheldon et al. 2020, McLachlan and Magrath 2020). However, due to the ecological importance of alarm calls in minimizing risk to group members, natural selection could promote stabilizing selection on alarm calls, resulting in homogenous alarm call structure across subspecies regardless of habitat and receiver. For this reason, we will also test whether Q. mexicanus songs differ between populations and ecological contexts across the US as natural selection likely promotes disruptive selection on song structure to facilitate subspecies recognition during mating season (Cruz-Yepez et al. 2020, Simpson et al. 2021). In this project we will enhance our understanding of the vocal repertoire of Q. mexicanus, by 1) recording and describing alarm calls and songs, 2) testing a null hypothesis that differing vocalizations will correlate with subspecies-specific soundscapes, and 3) test an alternative hypothesis that vocal signal characteristics correlate with range expansion. We will improve the description of vocalizations by recording vocalizations from each subspecies and analyzing the tone, range and pitch of vocalizations using spectrograms generated with Raven Lite 2.0 (Cornell Lab of Ornithology). Recording of alarm calls will take place during the non-breeding season, and of songs during the breeding season. We will only record alarm calls during the non-breeding period to avoid differences associated with reproduction. For our first objective, a phylogenetic principal component analysis (PPCA) will be conducted to identify correlations among measures of vocalization structure across subspecies while accounting for phylogenetic history. For our second objective, a phylogenetic generalized least squares analysis (PGLS) will be conducted to determine if subspecies vocalization characteristics are explained by social and habitat contexts within a phylogenetic context. To test whether vocalizations have functionally diverged and to help explain differences in range expansion, we will conduct a reciprocal playback experiment measuring responsiveness to recordings from within each subspecies compared to those from other subspecies. We will use the results of the PPCA and playback experiment to test whether vocal signal characteristics (both signal and response) are significant regional drivers of predicted distributions for Q. mexicanus in the US using an ensemble distribution model. If vocal signal skill is learned from context-dependent experiences unique to each subspecies (i.e., in line with the acoustic adaptation hypothesis), then individuals should share vocal characteristics with and respond to the signals of their own subspecies but not to signals of other subspecies. Tone, range, and pitch of vocalizations as well as low responsiveness will be a significant explanatory variable in all regional models (i.e., differences in vocal signals will distinguish subspecies distributions). However, if differences in regional models are due to variation in responsiveness according to subspecies, then skill in vocal communication could contribute to differences in range expansion among subspecies....

Contingency and determinism in the evolution of bird song sound frequency

Sexual signals are archetypes of contingent evolution: hyper-diverse across species, often evolving fast and in unpredictable directions. It is unclear to which extent their evolutionary unpredictability weakens deterministic evolution, or takes place bounded by deterministic patterns of trait evolution. We compared the evolution of sound frequency in sexual signals (advertisement songs) and non-sexual social signals (calls) across > 500 genera of the crown songbird families. Contrary to the acoustic adaptation hypothesis, we found no evidence that forest species used lower sound frequencies in songs or calls. Consistent with contingent evolution in song, we found lower phylogenetic signal for the sound frequency of songs than calls, which suggests faster and less predictable evolution, and found unpredictable direction of evolution in lineages with longer songs, which presumably experience stronger sexual selection on song. Nonetheless, the most important deterministic pattern of sound frequency evolution—its negative association with body size—was stronger in songs than calls. This can be explained by songs being longer-range signals than most calls, and thus using sound frequencies that animals of a given size produce best at high amplitude. Results indicate that sexual selection can increase aspects of evolutionary contingency while strengthening, rather than weakening, deterministic patterns of evolution.

Pup ultrasonic isolation calls of six gerbil species and the relationship between acoustic traits and body size

Among Gerbillinae rodents, ultrasonic calls of adults of small-sized species are typically higher frequency than those of adults of large-sized species. This study investigates whether a similar relationship can be found in pups of six gerbil species ( Dipodillus campestris , Gerbillus perpallidus , Meriones unguiculatus , Meriones vinogradovi , Sekeetamys calurus and Pachyuromys duprasi ). We compared the average values of acoustic variables (duration, fundamental and peak frequency) of ultrasonic calls (20 calls per pup, 1200 in total) recorded from 6- to 10-day-old pups (10 pups per species, 60 in total) isolated for 2 min at 22°C and then weighed and measured for body variables. The longest calls (56 ± 33 ms) were found in the largest species, and the highest frequency calls (74.8 ± 5.59 kHz) were found in the smallest species. However, across species, call duration (ranging from 56 to 159 ms among species) did not display a significant relationship with pup body size; and, among frequency variables, only the minimum fundamental frequency depended on pup body size. Discriminant analysis assigned 100% of calls to the correct species. The effect of species identity on the acoustics was stronger than the effect of body size. We discuss these results with the hypotheses of acoustic adaptation, social complexity, hearing ranges and phylogeny.