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The absolute threshold of hearing (ATH) is the minimum sound level of a pure tone that an average human ear with normal hearing can hear with no other sound present. The absolute threshold relates to the sound that can just be heard by the organism.〔Durrant J D., Lovrinic J H. 1984. ''Bases of Hearing Sciences''. Second Edition. United States of America: Williams & Wilkins〕〔Gelfand S A., 2004. ''Hearing an Introduction to Psychological and Physiological Acoustics''. Fourth edition. United States of America: Marcel Dekker〕 The absolute threshold is not a discrete point, and is therefore classed as the point at which a sound elicits a response a specified percentage of the time.〔 This is also known as the auditory threshold. The threshold of hearing is generally reported as the RMS sound pressure of 20 micropascals, or 0.98 pW/m2 at 1 atmosphere and 25 °C.〔RMS pressure can be converted to sound intensity using , where ρ is the density of air and is the speed of sound〕 It is approximately the quietest sound a young human with undamaged hearing can detect at 1,000 Hz.〔Gelfand, S A., 1990. ''Hearing: An introduction to psychological and physiological acoustics''. 2nd edition. New York and Basel: Marcel Dekker, Inc.〕 The threshold of hearing is frequency dependent and it has been shown that the ear's sensitivity is best at frequencies between 1 kHz and 5 kHz.〔 == Psychophysical methods for measuring thresholds == Measurement of the absolute hearing threshold provides some basic information about our auditory system.〔 The tools used to collect such information are called psychophysical methods. Through these, the perception of a physical stimulus (sound) and our psychological response to the sound is measured.〔Hirsh I J.,1952. "The Measurement of Hearing". United States of America: McGraw-Hill.〕 Several psychophysical methods can measure absolute threshold. These vary, but certain aspects are identical. Firstly, the test defines the stimulus and specifies the manner in which the subject should respond. The test presents the sound to the listener and manipulates the stimulus level in a predetermined pattern. The absolute threshold is defined statistically, often as an average of all obtained hearing thresholds.〔 Some procedures use a series of trials, with each trial using the ‘single-interval “yes”/”no” paradigm’. This means that sound may be present or absent in the single interval, and the listener has to say whether he thought the stimulus was there. When the interval does not contain a stimulus, it is called a "catch trial".〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Absolute threshold of hearing」の詳細全文を読む スポンサード リンク
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