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Sensitivity to Differences in Intensity between Repeated Bursts of Noise
Abstract
Thresholds for the detection of a decrement in noise intensity between repeated bursts of noise were determined as a function of the duration of the interval between successive bursts. The results indicate a critical duration (55 milliseconds) between successive noise bursts: (1) above which, the differential threshold is constant and independent of the interval between successive bursts and (2) below which, the differential threshold increases proportionately as the interval between successive bursts decreases. Since an equivalent critical interval has previously been obtained by several different independent measures of auditory persistence, the observed deterioration of differential sensitivity is interpreted in terms of the overlap or addition of auditory persistence with the direct effects of stimulation.
... The intensity DL for wideband noises varies from about 0.4 to 0.8 dB depending on the type of noise (Miller, 1947;Pollack, 1951) and rises up to 1 to 3 dB for octave band noises depending on the center frequency of the noise (Small, Bacon and Fozard, 1959). ...
Audition Audition is the act of hearing a sound in response to acoustic waves or mechanical vibrations acting on a body. Sound also may result from direct electrical stimulation of the nervous system. The physical stimuli that are, or may become, the sources of sound are called auditory stimuli. The human response to the presence of auditory stimulus and its basic physical characteristics of sound intensity, frequency, and duration is called auditory sensation. The three basic auditory sensations are loudness, pitch, and perceived duration, but there are many others. Auditory sensation forms the basis for discrimination between two or more sounds and may lead to some forms of sound classification (e.g., labeling sounds as pleasant or unpleasant). However, auditory sensation does not involve sound recognition, which requires a higher level of cognitive processing of the auditory stimuli. This higher level processing forms a conceptual interpretation of the auditory stimulus and is referred to as auditory perception. Auditory perception involves association with previous experience and depends on the adaptation to the environment and expected utility of the observation. Depending on the level of cognitive processing, auditory perception may involve processes of sound classification, e.g., on speech and non-speech sounds, sound recognition, or sound identification. More complex cognitive processing also may include acts of reasoning, selection, mental synthesis, and concept building involving auditory stimuli but extends beyond the realm of audition. The study of audition is called psychoacoustics (psychological acoustics). Psychoacoustics falls within the domain of cognitive psychophysics, which is the study of the relationship between the physical world and its mental interpretation. Cognitive psychophysics is an interdisciplinary field that integrates classical psychophysics (Fechner, 1860), which deals with the relationships between physical stimuli and sensory response (sensation), and with elements of cognitive psychology, which involve interpretation of acting stimuli (perception). In general, cognitive psychophysics is concerned with how living organisms respond to the surrounding environment (Stevens, 1972b). For the above reasons, Neuhoff (2004) refers to modern psychoacoustics as ecological psychoacoustics. In general, all content of our experience can be ordered by quantity, quality, relation, and modality (Kant, 1781). These experiences are reflected in perceptual thresholds, various forms of comparative judgments, magnitude estimation, emotional judgments, and scaling. These characteristics define the realm of psychoacoustics and, more generally, psychophysics. Various types of cognitive measurements and methodological issues addressing psychophysical relationships are described in Chapter 15, Cognitive Factors in Helmet-Mounted Displays, and are not repeated here. The current chapter presents psychoacoustic relationships and builds upon the information on the anatomy and physiology of the auditory system presented in Chapter 8, Basic Anatomy of the Hearing System, and Chapter 9, Auditory Function. It describes a variety of auditory cues and metrics that are used to derive an understanding of the surrounding acoustic space and the sound sources operating within its limits. Understanding how a particular sound is likely to be perceived in a particular environment is necessary for the design of effective auditory signals and to minimize the effects of environmental noise and distracters on performance of audio helmet-mounted displays (HMDs). Psychoacoustics provides the basic conceptual framework and measurement tools (thresholds and scales) for the discussion and understanding of these effects. The main physical quantity that elicits auditory response is time-varying sound pressure. The other quantities are time-varying force (bone conduction hearing) and time-varying (alternating current [AC]) voltage (electric hearing). The unit of sound pressure is the Pascal (Pa), which is equal to a Newton/meter 2 (N/m 2), and the range of sound pressures that can be heard by humans extends from about 10 -5 Pa to 10 2 Pa. The large range of values needed to describe the full range of audible sound pressure makes the use of Pascals, or other similar linear units, very cumbersome. In addition, human auditory perception is far from linear. Human perception is relative by nature and logarithmic in general, i.e., linear changes in the amount of stimulation cause logarithmic changes in human perception (Emanuel, Letowski and Letowski, 2009). Therefore, sound pressure frequently is expressed in psychoacoustics on a logarithmic scale known as the decibel scale from the name of its unit, the decibel (dB). The decibel scale has a much smaller range than the sound pressure scale and more accurately represents human reaction to sound. Sound pressure expressed in decibels is called sound pressure level. Sound pressure level (SPL) and sound pressure (p) are related by the equation:) (log 20 (dB)
... The Weber fractions for length and loudness are approximately 2% and 4.8% 2 , respectively (Laming, 1986; Teghtsoonian, 1971), suggesting that people are less sensitive to changes in tones of varying loudness than lines of varying length. Such explanations seem implausible, however, because in all of our experiments, stimulus separation was well above the Weber fraction, and research has shown that increasing separation between stimuli either has no effect at all (see e.g., Gravetter & Lockhead, 1973; Pollack, 1951) or results in a quite small improvement in performance (see e.g., Lacouture, 1997; Stewart et al., 2005). ...
In most of the long history of the study of absolute identification--since Miller's (1956) seminal article--a severe limit on performance has been observed, and this limit has resisted improvement even by extensive practice. In a startling result, Rouder, Morey, Cowan, and Pfaltz (2004) found substantially improved performance with practice in the absolute identification of line lengths, albeit for only 3 participants and in a somewhat atypical paradigm. We investigated the limits of this effect and found that it also occurs in more typical paradigms, is not limited to a few virtuoso participants or due to relative judgment strategies, and generalizes to some (e.g., line inclination and tone frequency) but not other (e.g., tone loudness) dimensions. We also observed, apart from differences between dimensions, 2 unusual aspects of improvement with practice: (a) a positive correlation between initial performance and the effect of practice and (b) a large reduction in a characteristic trial-to-trial decision bias with practice.
Hatten wir bisher den Weg der informationstragenden Signale ausschließlich im Bereich der physikalischen Übertragungsmedien verfolgt, so wollen wir nun das Schicksal der Signale beim empfangsseitigen Kommunikationspartner, dem Perzipienten, betrachten, d. h. im psychophysiologischen Bereich.
Als Schallempfänger bezeichnet man Geräte, mit deren Hilfe Schallschwingungen in Schwingungen anderer Energieform, insbesondere in mechanische oder elektrische Schwingungen umgesetzt werden können. Von besonderer praktischer Bedeutung sind die elektrischen Schallempfänger, mit ihrer Hilfe kann Schall über Leitungen oder drahtlos in die Ferne geleitet werden, insbesondere kann er auch in hochwertiger Weise aufgezeichnet werden. Fast alle modernen Geräte zur Messung der Schallstärke oder zur Analyse von Schallvorgängen besitzen elektrische Schallempfänger; die Schallschwingungen werden zunächst in elektrische Schwingungen umgesetzt, die dann nach entsprechender Verstärkung mit den hochwertigen Mitteln der elektrischen Meßtechnik untersucht werden.
Der Bau des menschlichen Ohres ist nicht nur vom physikalischen, sondern auch vom technischen Standpunkt außerordentlich lehrreich. Die Natur hat hier einen Apparat geschaffen, der an Leistungsfähigkeit und Zweckmäßigkeit unsere modernsten technischen Einrichtungen übertrifft und immer wieder wertvolle Hinweise für Entwicklungsarbeiten liefert.
The rate of decay of auditory sensation was investigated by measuring the minimum silent interval that must be introduced between two noise pulses to be perceived. The value of this critical time Λt was determined for different intensity levels of both the first and the second pulse. It is shown that in this case the sensation level of the second pulse may be considered as a very good approximation of the level of auditory sensation after Λt, due to the first pulse. From the experiments, we may conclude (1) expressed in dB as a function of log t, the decay of sensation is represented by a straight line; (2) independent of the sensation level of the stimulating sound, the hearing threshold is reached at the same time of about 200–300 msec. These results are compared with other experiments and the differences are discussed.
The current study was designed to see how hearing-impaired individuals judge level differences between speech sounds with and without hearing amplification. It was hypothesized that hearing aid compression should adversely affect the user's ability to judge level differences.
Thirty-eight hearing-impaired participants performed an adaptive tracking procedure to determine their level-discrimination thresholds for different word and sentence tokens, as well as speech-spectrum noise, with and without their hearing aids. Eight normal-hearing participants performed the same task for comparison.
Level discrimination for different word and sentence tokens was more difficult than the discrimination of stationary noises. Word level discrimination was significantly more difficult than sentence level discrimination. There were no significant differences, however, between mean performance with and without hearing aids and no correlations between performance and various hearing aid measurements.
There is a clear difficulty in judging the level differences between words or sentences relative to differences between broadband noises, but this difficulty was found for both hearing-impaired and normal-hearing individuals and had no relation to hearing aid compression measures. The lack of a clear adverse effect of hearing aid compression on level discrimination is suggested to be due to the low effective compression ratios of currently fit hearing aids.
Weber's law holds at least an 80 dB range for intensity discrimination of 200 msec bursts of noise. Weber's law holds over a comparable range when information regarding intensive differences is effectively restricted to a limited frequency region by the addition of a relatively intense band reject noise. In particular, no failure of Weber's law is observed at intensities for which the discharge rates of fibers innervating the frequency region of the stopband are presumably saturated. These results do not support the generally accepted notion that a spread of excitation along the cochlear partition with increasing intensity is necessary for the auditory system to maintain its large dynamic range.
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