The formation of auditory images from complex sound sources is an important function of the human auditory system. Several physical characteristics of complex sounds have been described to be important for the formation of auditory images. In this project, we describe experiments directed at gaining an understanding of the role of harmonicity and intensity in auditory image formation. Intensity can refer to the overall sound level of a stimulus or it may refer to the intensity profile of a stimulus. Harmonicity is closely related to the perception of pitch which is an important perception of many complex sounds, including speech and music. We will specifically focus on the auditory processing of stimulus features related to harmonicity and intensity of different types of noise signals, particularly rippled noises and bandlimited noises. Rippled noises produce the perception of pitch in humans and can be broadband or bandlimited signals. The proposed experiments involve human psychophysics and computer simulations, animal behavior, and single neuron recording. In human psychophysical experiments, we will continue to define the sensory and perceptual capabilities of the auditory system for processing spectrally rippled stimuli, including iterated-rippled noises and log-rippled stimuli. These studies will also include simulations using the Pulse- Ribbon Model of Roy Patterson. In animal experiments, we will study rippled noise processing in the chinchilla using positive reinforcement, psychophysical procedures which will allow us to define the sensory capabilities of this animal for processing rippled noise stimuli. As part of this effort, we will also study the ability of the chinchilla to detect intensity increments of bandlimited noise. Finally, we will study the neural representations of the temporal and spectral characteristics of rippled noises and bandlimited noises in the discharge patterns of neurons in the chinchilla cochlear nucleus. These studies will allow us to compare the results from the chinchilla psychophysical experiments to neuronal responses in the chinchilla cochlear nucleus and to human psychophysical data. These experiments will provide important insights into the neural processing of harmonicity and intensity of complex sounds in humans.

Project Start
Project End
Budget Start
Budget End
Support Year
11
Fiscal Year
1995
Total Cost
Indirect Cost
Name
Loyola University Chicago
Department
Type
DUNS #
City
Chicago
State
IL
Country
United States
Zip Code
60660
Shofner, William P; Whitmer, William M; Yost, William A (2005) Listening experience with iterated rippled noise alters the perception of 'pitch' strength of complex sounds in the chinchilla. J Acoust Soc Am 118:3187-97
Shofner, William P; Selas, George (2002) Pitch strength and Stevens's power law. Percept Psychophys 64:437-50
Shofner, William P (2002) Perception of the periodicity strength of complex sounds by the chinchilla. Hear Res 173:69-81
Ma, W-L D; Fay, R R (2002) Neural representations of the axis of acoustic particle motion in nucleus centralis of the torus semicircularis of the goldfish, Carassius auratus. J Comp Physiol A Neuroethol Sens Neural Behav Physiol 188:301-13
Weeg, M S; Fay, R R; Bass, A H (2002) Directionality and frequency tuning of primary saccular afferents of a vocal fish, the plainfin midshipman (Porichthys notatus). J Comp Physiol A Neuroethol Sens Neural Behav Physiol 188:631-41
Fay, Richard R; Edds-Walton, Peggy L (2002) Preliminary evidence for interpulse interval selectivity of cells in the torus semicircularis of the oyster toadfish (Opsanus tau). Biol Bull 203:195-6
Trout, J D (2001) The biological basis of speech: what to infer from talking to the animals. Psychol Rev 108:523-49
Fay, R R (2000) Spectral contrasts underlying auditory stream segregation in goldfish (Carassius auratus). J Assoc Res Otolaryngol 1:120-8
Shofner, W P (2000) Comparison of frequency discrimination thresholds for complex and single tones in chinchillas. Hear Res 149:106-14
Shofner, W P (1999) Responses of cochlear nucleus units in the chinchilla to iterated rippled noises: analysis of neural autocorrelograms. J Neurophysiol 81:2662-74

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