The Laboratory of Comparative Psychoacoustics
Department of Psychology University of Maryland College Park, MD 20742 Tel (301) 405-5940 Fax (301) 314-9566 |
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EDUCATION:
Ph.D. - Duke University, 1995
M.S. - University of Wisconsin - Milwaukee, 1989
A.B. - Cornell University, 1984
SCIENTIFIC MEMBERSHIPS:
CHICKADEE SONG PERCEPTION:
I am interested in bioacoustics and the evolution of animal communication systems. In my past and current studies I explore the perceptual mechanisms that govern song and call detection, discrimination, and recognition in birds. My dissertation work addressed the question of how birds used acoustic frequency (pitch) information in identifying conspecifics. Frequency perception can be divided into two broad categories: relative and absolute. Relative perception involves the ability to recognize relationships between the frequencies of different tones or song notes, while absolute frequency perception refers to the ability to identify the frequency of individual song notes without an external reference. Several species of North American chickadees sing very simple songs, consisting principally of unmodulated pure tones. Carolina chickadee (Parus carolinensis) songs are characterized by a succession of notes that alternate between high (5.4 - 7.0 kHz) and low (3.0 - 4.2 kHz) frequency ranges. Using song playback experiments in the field, I showed that energy in note-typical high and low frequency ranges provides the primary cues for song recognition in this species, and that the transitional sequences (contours) between note frequencies play a supplementary role. A perceptual "gap" exists between high and low note frequency ranges (4.2 - 5.4 kHz) in which notes are not recognized in the context of song. Two other species, black-capped chickadees (P. atricapillus) and mountain chickadees (P. gambeli), are sympatric over parts of their geographic ranges, and they may sing very similar songs. An examination of variation in song, combined with preliminary playback studies suggest that absolute frequency cues predominate again, in this case as a means of differentiating conspecific from very similar heterospecific songs.
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| Carolina chickadee song |
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| Black-capped chickadee song | Mountain chickadee song |
THE PERCEPTION OF COMPLEX SOUNDS BY BIRDS:
As a postdoc, I am currently undertaking several projects examining the comparative aspects of complex sound perception in birds. Much of this work involves the zebra finch (Taeniopygia guttata) (see our zebra finch page), a small colonial member of the family Estrildidae that produces spectrally complex vocalizations and has become a favorite songbird model for neurobiologists. Using operant conditioning, we have discovered that zebra finches are especially sensitive to mistunings of single components in harmonic sounds that mimic properties of their own natural harmonic calls (see below). Most recently, as a first step in comparative studies, I have begun measuring the behavioral audiogram and masked thresholds in a related estrildid, the red-billed firefinch (Lagonosticta senegala). This species, unlike the zebra finch, produces pure-tone songs and calls. At the same time, I am exploring the perceptual basis for the enhanced sensitivity to harmonic mistuning in zebra finches. Other ongoing studies include discrimination tests of spectro-temporally degraded songs, an examination of time and spectral window size in finches and budgerigars, sensitivity to the phase of components in a harmonic stimulus, and studies of rippled noise perception as a means of simulating spectral properties of these calls using a temporally modified stimulus.
Example mistuned harmonic stimuli - 500 Hz fundamental with 12 harmonics
No mistuning
Time waveform |
25Hz (1%) mistuning
of 5th harmonic
Time waveform |
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THE EFFECTS OF NOISE ON ACOUSTIC COMMUNICATION IN BIRDS:
I have recently become interested in the effects of noise on the perception of species-specific vocalizations in birds. By using standard stimuli such as pure tones and white noise maskers, we already know much about the general effects of noise on the avian auditory system. However, little is known regarding the detrimental effects that both natural and anthropocentric noise may pose for a bird's ability to communicate effectively in a particular acoustic environment. These effects are of special concern for sensitive species in habitats near loud noise sources like highways and military bases. I am presently involved in using two approaches to evaluate the effects of noise on auditory perception in birds: operant discrimination testing using natural calls with shaped noise, and non-invasive auditory brainstem physiology. We have been using operant studies to test the ability of zebra finches, budgerigars (Melopsittacus undulatus), and canaries (Serinus canaria) to detect calls of each species in white noise maskers and noise shaped to simulate a traffic spectrum. These studies will be extended to involve other species tested on their own natural vocalizations in a variety of noise spectra as a means of assessing the effects of masking on the detection, discrimination, and recognition of conspecific sounds under ecologically relevant circumstances. See our page on the effects of environmental noise on hearing and communication for more information on these studies. We have also been using the auditory evoked potential, or auditory brainstem response (ABR), to estimate the hearing ability of birds. We are currently using this technique with downy woodpeckers (P. pubescens) and hairy woodpeckers (P. villosus) as models for evaluating the hearing abilities of a close relative, the red-cockaded woodpecker (Picoides borealis), a critically endangered species. The ultimate goal of these two approaches is to generate a predictive model for evaluating the impact of noise on birds communicating in their natural habitats.
INVITED LECTURES:
Lohr, B., Brittan-Powell, E. F., Dooling, R. J., & Pater, L. (May, 2000). Auditory sensitivity in woodpeckers. Special Session: Animal Bioacoustics - Acoustical Society of America: Atlanta, GA.Lohr, B. (February, 1998). Songs of the Paridae: A parody of song. Biological Research Seminar Series - National Zoological Park / Smithsonian Institute: Washington, DC.
Lohr, B. (December, 1997). Acoustic perceptual mechanisms and song recognition in the Paridae. Zoology Department Seminar - University of Maryland: College Park, MD.
Lohr, B. & Dooling, R. J. (July, 1997). The detection of inharmonicity in complex harmonic sounds by zebra finches and budgerigars. Northeast Regional Birdsong Workshop - Cornell University: Ithaca, NY.
Lohr, B. (November, 1995). The role of frequency cues in song recognition by Carolina chickadees. Neuroendocrinology and Behavior Seminar - Johns Hopkins University: Baltimore, MD.
RECENT MEETING PRESENTATIONS (last 5 years):
Lohr, B., Bartone, S., & Dooling, R. J. (2000). The discrimination of fine-scale temporal changes in call-like harmonic stimuli by birds. Association for Research in Otolaryngology: St. Petersburg, FL.Dent, M. L., Brittan-Powell, E. F., Dooling, R. J., Lohr, B., & Pater, L. (2000). Estimating equal loudness contours of animals. Acoustical Society of America: Atlanta, GA.
Wright, T. F., Lohr, B., & Dooling, R. J. (2000). The effect of masking noise on the discrimination of conspecific and heterospecific vocalizations in birds. Association for Research in Otolaryngology: St. Petersburg, FL.
Pater, L., Delaney, D., Hayden, T., Dooling, R. J., & Lohr, B. (1999). Military training noise impacts on the endangered red-cockaded woodpecker: preliminary results. Acoustical Society of America: Columbus, OH.
Dent, M. L., Dooling, R. J., Leek, M. R., Mavilia, M. R., & Lohr, B. (1999). Comparative studies of masking by harmonic complexes in several species of birds. Acoustical Society of America: Columbus, OH.
Lohr, B., Wright, T. F., & Dooling, R. J. (1999). The effect of noise maskers on the detection of avian vocalizations. Animal Behavior Society. Lewisburg, PA.
Hughes, M., Nowicki, S., Hailman, J., Woolley, S., & Lohr, B. (1999). The role of development in the evolution of vocalizations: call notes in black-capped, Carolina, and mountain chickadees. Animal Behavior Society: Lewisburg, PA.
Lohr, B., Wright, T. F., & Dooling, R. J. (1999). The detection of conspecific and heterospecific calls in noise by birds. Joint meeting of the Acoustical Society of America and the Convention of the European Acoustics Association: Forum Acusticum: Berlin, Germany.
Lohr, B. & Dooling, R. J. (1999). Hearing in the red-billed firefinch (Lagonosticta senegala): An estrildid finch with pure-tone vocalizations. Association for Research in Otolaryngology: St. Petersburg, FL.
Lohr, B., Dooling, R. J., Theunissen, F., & Doupe, A. (1998). Discrimination of degraded conspecific song in zebra finches (Taeniopygia guttata). Acoustical Society of America: Norfolk, VA.
Lohr, B., Dooling, R. J., Theunissen, F., & Doupe, A. (1998). Auditory discrimination of degraded songs in zebra finches (Taeniopygia guttata). 5th International Congress of Neuroethology: San Diego, CA.
Lin, J.-Y., Dooling, R. J., Lohr, B., & Leek, M. R. (1998). The temporal resolution of the avian auditory system. Association for Research in Otolaryngology: St. Petersburg, FL.
Lohr, B., Wiebe, M. O., & Lein, M. R. (1997). Song discrimination in sympatric mountain and black-capped chickadees. Animal Behavior Society: College Park, MD.
Lohr, B. & Dooling, R. J. (1997). The detection of inharmonicity in complex tones by zebra finches (Taeniopygia guttata) and budgerigars (Melopsittacus undulatus). Association for Research in Otolaryngology: St. Petersburg, FL.
Lohr, B. & Dooling, R. J. (1996). Discrimination of spectral features in complex sounds by zebra finches (Taeniopygia guttata) and budgerigars (Melopsittacus undulatus). Animal Behavior Society: Flagstaff, AZ.
Lohr, B., Dooling, R. J., Amagai, S., & Shamma, S. (1996). Discrimination of synthetic harmonic stimuli by zebra finches (Taeniopygia guttata) and budgerigars (Melopsittacus undulatus). Association for Research in Otolaryngology: St. Petersburg, FL.
Lohr, B. (1995). Gaps, ranges, and sequencing in bird song: Acoustic frequency cues and song recognition in Carolina chickadees. Society for Integrative and Comparative Biology: Washington, DC.
Lohr, B. (1995). A comparison of song features in three species of North American chickadees. 24th International Ethological Conference: Honolulu, HI.
COURSES TAUGHT:
- Fall 2000: Department of Biology, University of Maryland
- Spring 1999: Department of Psychology, University of Maryland
- Summers 1996, 1997, 1998: Department of Biology, University of Maryland
Fall 1997: Department of Psychology, University of Maryland
Winter 1998 (intersession): Department of Biology, University of Maryland
Fall 1987 (instructor for 1/2 semester): Department of Biological Sciences, University of Wisconsin - Milwaukee
blohr@psyc.umd.edu