1aAB4 – What does a Greater Prairie-Chicken sound like? It’s not your typical cock-a-doodle-doo!

Cara Whalen – cara.whalen@huskers.unl.edu
Mary Bomberger Brown – mbrown9@unl.edu
Larkin Powell – lpowell3@unl.edu
Jennifer Smith – jsmith60@unl.edu
University of Nebraska – Lincoln

School of Natural Resources
3310 Holdrege Street
Lincoln, NE 68583

Edward J. Walsh – Edward.Walsh@boystown.org
JoAnn McGee – JoAnn.McGee@boystown.org
Boys Town National Research Hospital
555 N. 30th Street
Omaha, NE 68131

Popular version of 1aAB4 The acoustic characteristics of greater prairie-chicken vocalizations
Presented Monday morning, October 27th, 2014
168th ASA Meeting, Indianapolis
Click here to read the abstract

It is 5 o’clock in the morning and only a hint of sunlight is visible on the horizon. Besides the sound of a light breeze swirling through the grass, all is quiet on the Nebraska prairie. Everything seems to be asleep. Then, suddenly, “whhooo-doo-doooohh” breaks the silence. The prairie-chickens have arrived.

The Greater Prairie-Chicken is a medium-sized grouse that lives on the prairies of central North America (Figure 1a) (Schroeder and Robb 1993). Prairie-chickens are well-known for their breeding activities in which the males congregate in groups each spring and perform elaborate courtship displays to attract females (Figure 1b). The areas where the males gather, called “leks,” are distributed across the landscape. Female prairie-chickens visit leks every morning to observe and compare males until a suitable one is chosen. After mating, females leave the leks to nest and raise their broods on their own, while the males remain on the leks and continue to perform courtship displays. Click the link to watch a video clip of prairie chickens lekking.

Prairie-Chicken Prairie-Chicken

Figure 1a: A male Greater Prairie-Chicken. Figure 1b: A male prairie-chicken performs a courtship display for a female.

These complex courtship behaviors do not occur in silence. Vocalization plays an important role in the mate choice behavior of prairie-chickens. As part of a larger study addressing the effects of electricity producing wind turbine farms on prairie-chicken ecology, we wanted to learn more about the acoustic properties of prairie-chicken calls. We did this by recording the sound of prairie-chicken vocalizations at leks in the Nebraska Sandhills. We visited the leks in the very early morning and set up audio recorders, which were placed close enough to prairie-chickens on their leks to obtain high quality recordings (Figure 2a). Sitting in a blind at the edges of leks (Figure 2b), we observed prairie-chickens while they were lekking and collected the audio recordings.

Prairie-Chickenwhalen_figure_2b - Prairie-Chicken

Figure 2a: We used audio recorders to record male prairie-chicken vocalizations at the leks. Figure 2b: We observed lekking prairie-chickens and recorded vocalizations by sitting in a blind at the edge of a lek.

Male Greater Prairie-Chickens use four prominent vocalizations while on the leks: the “boom,” “cackle,” “whine” and “whoop.” The four vocalizations are distinct and serve different purposes.

The boom is used as part of the courtship display, so one function is to attract mates. Booms travel a long distance across the prairie, so another purpose of the call is to advertise lek location to other prairie-chickens (Sparling 1981, 1983). Click to listen to a boom sound clip

or to watch a boom video clip we recorded at the leks.

The “cackles” are short calls typically given in rapid succession. Prairie-chickens use the cackle as an aggressive or territorial call (Sparling 1981, 1983) or as a warning to alert other prairie-chickens of potential danger, such as an approaching prairie falcon, coyote or other predator. Click to listen to a cackle sound clip.

The “whine” is slightly longer in duration than the cackle; whines and cackles are often used together. The purpose of the whine is similar to that of the cackle. It serves as an aggressive and territorial call, although it is thought that whines are somewhat less aggressive than cackles (Sparling 1981, 1983). Click to listen to a whine sound clip

or to watch a video clip of cackles and whines (the cackles are the shorter notes and the whines are the longer notes).

The “whoop” is used for mate attraction. Males typically use the whoop when females are present on the lek (Sparling 1981, 1983). Click to listen to a whoop sound clip

or to watch a whoop video clip.

We measured acoustic characteristics of the vocalizations captured on the recordings so we could evaluate their features in detail. We are using this information about the vocalizations in a study of the effects of wind turbine sound on Greater Prairie-Chickens (Figure 3). We hope to determine whether the vocalizations produced by prairie-chickens near a wind farm are different in any way from those produced by prairie-chickens farther away. For example, do the prairie chickens near wind turbines call at a higher pitch in response to wind turbine sound? Also, do the prairie chickens near wind turbines vocalize louder? Ultimately we would like to know if components of the prairie-chickens’ vocalizations are masked by the sounds of the wind turbines.

Prairie-Chicken

Figure 3: We are conducting a study of the effects of wind turbine noise on Greater Prairie-Chickens.

The effect of anthropogenic noise is an issue not limited to Greater Prairie-Chickens and wind turbines. As humans create increasingly noisy landscapes through residential and industrial development, vehicle traffic, air traffic and urban sprawl, the threats posed to birds and other wildlife are likely to be significant. It is important to be aware of the potential effects of anthropogenic sound and find ways to mitigate those effects as landscapes become noisier.

 

References:

Schroeder, M. A., and L. A. Robb. 1993. Greater Prairie-Chicken (Tympanuchus cupido). In The Birds of North America, no. 36 (A. Poole, P. Stettenheim, and F. Gill, Eds.). Academy of Natural Sciences, Philadelphia, and American Ornithologists’ Union, Washington, D.C.

Sparling, D. W. 1981. Communication in prairie grouse. I. Information content and intraspecific functions of principal vocalizations. Behavioral and Neural Biology 32:463-486.

Sparling, D. W. 1983. Quantitative analysis of prairie grouse vocalizations. Condor 85:30-42.

5aNS5 – Acoustic absorption of green roof samples commercially available in southern Brazil

Stephan Paul – stephan.paul@eac.ufsm.br
Undergrad
Program Acoustical Engineering
Fed. University of Santa Maria
Santa Maria, RS, Brazil

Ricardo Brum – ricardo.brum@eac.ufsm.br
Undergrad
Program Acoustical Engineering
Fed. University of Santa Maria
Santa Maria, RS, Brazil

Andrey Ricardo da Silva – andrey.rs@ufsc.br
Fed. University of Santa Catarina
Florianópolis, SC, Brazil

Tenile Rieger Piovesan – arqui.tp@gmail.com
Graduate program in Civil Engineering
Fed. University of Santa Maria
Santa Maria, RS, Brazil

Investigations into the benefits of green roofs have shown that such roofs provide many environmental benefits, such as thermal conditioning, air cleaning and rain water absorption. Analysing the way green roofs are usually constructed suggests that they may have also two interesting acoustical properties: sound insulation and sound absorption. The first property would provide protection of the house’s interior from environmental noise produced outside the house. Sound absorption, on the other hand, would reduce the environmental noise in the environment itself, by dissipating sound energy that is being irradiated on to the roof from environmental noise sources. Thus, sound absorption can help to reduce environmental noise in urban settings. Despite of being an interesting characteristic, information regarding acoustic properties of green roofs and their effects on the noise environment is still sparse. This work looked into the sound absorption of two types of green roofs commercially available in Brazil: the alveolar and the hexa system.

Fig 1: illustration of the alveolar system (left) and hexa system (right)

Sound absorption can be quantified by means of a sound absorption coefficient α, which ranges between 0 and 1 and is usually a function of frequency. Zero means that all incident energy is being reflected back into the environment and α = 1 means that all energy is being dissipated in the layers of the material, here the green roof. To find out how much sound energy the alveolar and the hexa system absorb standardized measurements were made in a reverberant chamber according to ISO-354 for different variations of both systems. The alveolar system used a thin layer of 2.5 cm of soil like substrate with and without grass and a 4 cm layer of substrate only. The hexa system was measured with layers of 4 and 6 cm of substrate without vegetation and 6 cm of substrate with a layer of vegetation of sedum. For all systems, high absorption coefficients (α > 0.7) were found for medium and high frequencies. This was expected due to the highly porous structure of the substrate. Nevertheless the alveolar system with grass, the alveolar system with 4 cm of substrate, the hexa with 6 cm of substrate and the hexa with sedum already provide high absorption for frequencies as low as 250 or 400 Hz. Thus, these green roofs systems are particularly interesting in urban settings, as traffic noise is usually low frequency noise and is hardly absorbed by smooth surfaces such as pavements or façades.

absorbtion coefficient

Fig 2: absorption coefficient of the alveolar samples (left) and hexa samples (right).

In the next step of this research is intended to make computational simulations of the noise reduction provided by the hexa and alveolar system in different noisy situations such as near airports or intense urban traffic.

4aAAa1 – Speech-in-noise recognition as both an experience- and signal-dependent process

Ann Bradlow – abradlow@northwestern.edu
Department of Linguistics
Northwestern UniversitY
2016 Sheridan Road
Evanston, IL 60208
Popular version of paper 4aAAa1

Presented Thursday morning, October 30, 2014
168th ASA Meeting, Indianapolis

Real-world speech understanding in naturally “crowded” auditory soundscapes is a complex operation that acts upon an integrated speech-plus-noise signal.   Does all of the auditory “clutter” that surrounds speech make its way into our heads along with the speech? Or, do we perceptually isolate and discard background noise at an early stage of processing based on general acoustic properties that differentiate sounds from non-speech noise sources and those from human vocal tracts (i.e. speech)?

We addressed these questions by first examining the ability to tune into speech while simultaneously tuning out noise. Is this ability influenced by properties of the listener (their experience-dependent knowledge) as well as by properties of the signal (factors that make it more or less difficult to separate a given target from a given masker)? Listeners were presented with English sentences in a background of competing speech that was either English (matched-language, English-in-English recognition) or another language (mismatched-language, e.g. English-in-Mandarin recognition). Listeners were either native or non-native listeners of English and were either familiar or unfamiliar with the language of the to-be-ignored, background speech (English, Mandarin, Dutch, or Croatian). Overall, we found that matched-language speech-in-speech understanding (English-in-English) is significantly harder than mismatched-language speech-in-speech understanding (e.g. English-in-Mandarin). Importantly, listener familiarity with the background language modulated the magnitude of the mismatched-language benefit On a smaller time scale of experience, we also find that this benefit is modulated by short-term adaptation to a consistent background language within a test session. Thus, we conclude that speech understanding in conditions that involve competing background speech engages experience-dependent knowledge in addition to signal-dependent processes of auditory stream segregation.

Experiment Series 2 then asked if listeners’ memory traces for spoken words with concurrent background noise remain associated in memory with the background noise. Listeners were presented with a list of spoken words and for each word they were asked to indicate if the word was “old” (i.e. had occurred previously in the test session) or “new” (i.e. had not been presented over the course of the experiment). All words were presented with concurrent noise that was either aperiodic in a limited frequency band (i.e. like wind in the trees) or a pure tone. Importantly, both types of noise were clearly from a sound source that was very different from the speech source. In general, words were more likely to be correctly recognized as previously-heard if the noise on the second presentation matched the noise on the first presentation (e.g. pure tone on both first and second presentations of the word). This suggests that the memory trace for spoken words that have been presented in noisy backgrounds includes an association with the specific concurrent noise. That is, even sounds that quite clearly emanate from an entirely different source remain integrated with the cognitive representation of speech rather than being permanently discarded during speech processing.

These findings suggest that real-world speech understanding in naturally “crowded” auditory soundscapes involves an integrated speech-plus-noise signal at various stages of processing and representation. All of the auditory “clutter” that surrounds speech somehow makes its way into our heads along with the speech leaving us with exquisitely detailed auditory memories from which we build rich representations of our unique experiences.

Important note: The work in this presentation was conducted in a highly collaborative laboratory at Northwestern University. Critical contributors to this work are former group members Susanne Brouwer (now at Utrecht University, Netherlands), Lauren Calandruccio (now at UNC-Chapel Hill), and Kristin Van Engen (now at Washington University, St. Louis), and current group member, Angela Cooper.