. Biophysical science. Biophysics. 18 Sound and the Ear /I : 3 change of pitch is noticed. These difference limens for frequency change are not independent of the sound pressure level. As the latter is lowered, the size of the difference limen for frequency changes increases. The presence of these finite steps, dignified by the term difference limens, resembles the phenomena well known in many phases of chemistry and physics, usually grouped under the classification quantum. 20cps lOOcps .Okc Frequency Figure. 7. Equal loudness contours after the American Stand- ards Association (1936). There
. Biophysical science. Biophysics. 18 Sound and the Ear /I : 3 change of pitch is noticed. These difference limens for frequency change are not independent of the sound pressure level. As the latter is lowered, the size of the difference limen for frequency changes increases. The presence of these finite steps, dignified by the term difference limens, resembles the phenomena well known in many phases of chemistry and physics, usually grouped under the classification quantum. 20cps lOOcps .Okc Frequency Figure. 7. Equal loudness contours after the American Stand- ards Association (1936). There is no general agreement on the exact shape of these curves, but the general flattening at higher sound pressure levels is always observed. After J. C. R. Licklider, in Handbook of Experimental Psychology, S. S. Stevens, ed. (New York: John Wiley & Sons, Inc., 1951). mechanics. Similarly, pure tone thresholds measured on individuals at very low frequencies suggest some type of quantum effect. Quantum effects do occur in acoustics, but the physical quanta of sound energy, known as phonons, are far too small to associate them in any way with hearing. Just as does the photon, the phonon has an energy, E, such that E = hv where h is Planck's constant and v is the frequency. A straightforward calculation will show the reader that, even at the threshold of hearing, a huge number of phonons must be reaching the ear each second, or even each cycle. This number is so large that the phonon cannot be responsible for the quantization observed in hearing studies. The hearing tests described in this section give no direct clues to the. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Ackerman, Eugene, 1920-. Englewood Cliffs, N. J. , Prentice-Hall
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