Roger B. Coles

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The acoustical properties of the external ear of the barn owl (Tyto alba) were studied by measuring sound pressure in the ear canal and outer ear cavity. Under normal conditions, pressure amplification by the external ear reaches about 20 dB between 3–9 kHz but decreases sharply above 10 kHz. The acoustic gain curve of the outer ear cavity alone is close to(More)
1. The maximum acoustic gain of the external ear inMacroderma gigas was found to be 25–30 dB between 5–8 kHz and inNyctophilus gouldi it reached 15–23 dB between 7–22 kHz. Pinna gain reached a peak of 16 dB near 4.5–6 kHz inM. gigas and 12–17 dB between 7–12 kHz inN. gouldi, with average gain of 6–10 dB up to 100 kHz. Pinna gain curves resemble that of a(More)
1. The neural audiogram of the common long-eared bat,Plecotus auritus was recorded from the inferior colliculus (IC). The most sensitive best frequency (BF) thresholds for single neurones are below 0 dB SPL between 7–20 kHz, reaching a best value of -20 dB SPL between 12–20 kHz. The lower and upper limits of hearing occur at 3 kHz and 63 kHz, respectively,(More)
Electroreceptors with sensitivity in the microvolt range, which mainly function to detect live prey, are well known in phylogenetically old fishes and some amphibians. In African mormyriform and South American gymnotiform fishes this sense has evolved to an active system using an electric organ as a source for impedance measurement of the environment and(More)
Most previous studies considering intraspecific differences in bat echolocation call frequency among geographic groups have related this to morphological features not directly involved in producing the characteristics of the emitted signal. We related a pattern of intraspecific call differences to the size of nasal chambers (estimated from radiographs of(More)
The frequency sensitivity of hearing in the grey svviftlet, Collocalia spodiopygia, was determined by neuronal recordings from the auditory midbrain (MLD). The most sensitive best frequency response thresholds occurred between 08 and 4*7 kHz, with the upper frequency limit near 6 kHz. Spectral analysis of echolocation click pairs revealed energy peaks(More)
Cues for directional hearing in mammals are traditionally based on inter-aural intensity differences (IIDs) established as a result of the diffraction of a progressive sound wave by the head and pinna, or on inter-aural time differences (ITDs) established because of the separation of the two ears in space. This ' dual hypothesis' has been extended to other(More)
Extracellular recordings were made from auditory units in the midbrain (NMLD) of the domestic fowl. Tonal stimuli delivered monaurally to either ear revealed that contralateral excitation predominated and was coupled with ipsilateral inhibition (EI, 46%), excitation (EE, 21%) or no effect (EO, 17%). Conventional V-shaped tuning curves were readily obtained(More)
Polymorphonuclear leukocytes (PMNs) from subjects diagnosed as having juvenile periodontitis (JP) have been categorized on the basis of their chemotactic (CTX) response to f-met-leu-phe (FMLP) when assayed concurrently with PMNs from periodontally healthy subjects (HP). When PMNs from JP groups demonstrating depressed CTX were assayed for lysosomal enzyme(More)