Auditory scales

It is well known that human sensitivity to the frequency scale is not linear for instance we know that musical relationships are clearly logarithmic. Studies into the low-level perception of sounds have resulted in a number of auditory scales, which define a new frequency range that is more in fine with the human sensitivity to sounds at different frequencies. 

The mel-scale was the product of experiments with sinusoids in which subjects were required to divide frequency ranges into sections. From this, a new scale was defined, in which one mel equalled one thousandth of the pitch of a 1-kHz tone [415]. The mapping from linear frequency to this scale is given by 

Further studies based on loudness (i.e. the perception of amplitude) found that a more accurate representation was one that had a linear response for lower frequencies, becoming logarithmic for higher frequencies. One popular scale based on this is the 

A tiiird popular scale is the equivalent rectangular bandwidth or ERB scale, which is measured from the ability to detect sinusoids in the presence of noise. From this auditory perception is described in terms of an equivalent rectangular bandwidth (ERB) as a ftinction of centre frequency [316]  

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Pitch The spacing of holes in a flange, or the angle of fan blades. That attribute of auditory sensation depending primarily on the frequency of the sound in terms of which sounds may be ordered on a scale extending from low to high. 

Spatial recall (windows-in-houses task) brief delay Supraspan auditory word list brief delay, written recall Verbal paired associates delayed recall Visuospatial memory (VIG) complex shape learning Visual paired associates delayed recall Wechsler Memory Scale (WMS) total spatial span Wechsler memory (WAIS) immediate and delayed paragraph recall... 

Research on the hearing process carried out by many people (see [Scharf, 1970]) led to a frequency analysis model of the human auditory system. The scale that the ear appears to use is called the critical band scale. The critical bands can be defined in various ways that lead to subdivisions of the frequency domain similar to the one shown in table 2.1. A critical band corresponds to both a constant distance on the cochlea and the bandwidth within which signal intensities are added to decide whether the combined signal exceeds a masked threshold or not. The frequency scale that is derived by mapping frequencies to critical band numbers is called the Bark scale. The critical band model is most useful for steady-state tones and noise. 

It is important to remember that this equation depends on the assumption that the quantizer is a fixed point, mid-tread converter with sufficient resolution so that the resulting quantization noise (enoise) is white. Furthermore, the input is assumed to be a full scale sinusoidal input. Clearly, few real world signals fit this description, however, it suffices for an upper bound. In reality, the RMS energy of the input is quite different due to the wide amplitude probability distribution function of real signals. One must also remember that the auditory system is not flat (see the chapter by Kates) and therefore SNR is at best an upper bound. 

Glenville M, Broughton R. Reliability of the Stanford Sleepiness Scale compared to short duration performance tests and the Wilkinson Auditory Vigilance task. In Passouant P, Oswald I, eds. Pharmacology of the States of Alertness. Oxford Pergamon, 1979 235-244. 

Another study was designed to determine how neural circuits are organized to provide a perception of sound. Specifically, Williamson wanted to find whether individuals have a tone map across the auditory cortex—that is, whether tones of different frequencies evoke neural activity at different locations. While Williamson s subjects listened to notes of a scale, the sensors hunted for magnetic field variations, and the researchers were able to monitor the movement of nerve impulses from cell group to cell group inside the brain. It appeared that the brain assigned equal numbers of neurons to each octave of the musical scale, much like the arrangement of keys on a piano. This... 

Health (NIMH) Workgroup WMS-R Visual Span Paced Auditory Serial Addition Test California Veibal Leammg Test Hamilton Depression Scale Speilberger State-Trait Arxiety Scale San Diego HIV Neurobehavioral Research Center (HNRC) Paced Auditory Serial Addition Test... 

Study (MACS) Rey Auditory Verbal Learnhig Test Trail Makhig Test Symbol Digit Modahties Test Gr ooved Pegboard Test CES Depression Scale... 

Fig. 8 Nissl stained section of primary auditory cortex, area 41, from a human cerebral hemisphere. In this cortical area there are obvious vertical strings of neurons arrows) separated by pale spaces that are largely occupied by the apical dendrites of pyramidal cells. Scale bar = 100 p,m...

Children s scores on the auditory comprehension scale of the Preschool Language Scale were also inversely associated with maternal-hair Hg concentrations (p = 0.0019). Scores declined approximately 2.5 points across the range of Hg concentrations. Additional analyses identified several outlier or influential data points, whose exclusion finm the analyses reduced the estimates of the Hg effect substantially, sometimes to nonsignificance. In the pilot phase of the SCDS, information was not collected on several key variables that frequently confoimd the association between neurotoxicant exposures and child development. Those variables are socioeconomic status, caregiver inteUigence, and qirality of the home environment. 

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