Laquer+H90+Science+Paper+1+ - Alan Laquer 89863832 Physics...

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Unformatted text preview: Alan Laquer 89863832 Physics H90 Measuring the Human Ability to Detect Frequency Difference Abstract Human subjects were used in a controlled acoustic environment with acoustically measured equipment in order to quantify certain characteristics of the human ability to detect frequency difference. These characteristics are the varying ability to detect frequency difference over the range of audible frequencies and the accuracy of naming frequency difference when it is detected. Data was gathered through recording subjects responses to questions of frequency difference. This data was then analyzed and trends cited with potential causes suggested. Introduction There has been a large amount of research designed to help explain the biological mechanisms which give the human ear its great acuteness. Work by Dr. Rod Nave of Georgia University combines the physics and biology involved in the human process of pitch resolution. Dr. Nave provides evidence that a combination of place theory, and sharpening mechanisms are used to produce a typical maximum sensitivity of 5 cents over the audible frequency range of 20 Hz 20 kHz. In place theory, hairs in the organ of Corti within the Cochlea are associated with specific acoustic response curves as a result of their location with relation to the length of the basilar membrane. Sharpening mechanisms cited by Dr. Nave include adjacent frequency response inhibition, in which the human mind is able to selectively filter out the signals from inner-ear hair cells providing medium responses when they are adjacent to cells providing higher responses, thus focusing the response. Theory Analyzing frequency differences requires an understanding of sound ratios. The 1Hz difference between 20Hz and 21Hz is more dramatic than that between 2000Hz and 2001Hz. In order to account for this, the unit of cents are used in calculating frequency differences. One cent is 1/1200 of an octave. Because of this, adding one cent to any frequency increases it by a fixed percentage rather than a fixed number of Hz. The equation on page 182 of the Rossing Moore & Wheeler book provides a means of converting a frequency ratio (R=f2/f1) to a number of cents (I): R=10^((I log2)/ 1200). This can be mathematically manipulated into the more simple form R=2^(I/1200). For calculating cents given two frequencies, the following equation can be used: I=log(R)*(1200/log2). Experiment Test Subjects and Equipment Used The experiment consisted of a series of tests, all of which were conducted using each of three different human subjects. Subject 1 is a 16 year old male, subject 2 is a 50 year old female, and subject 3 is a 50 year old male. The testing equipment used was an application called Test Tone Generator running on a PC with Windows XP and a Sound Blaster Live! sound card outputting all sound to ear-insulating Koss UR-30 headphones which the subject wore while being tested. All testing was conducted in a well insulated room with background noise at a minimum. The Test Tone Generator application is capable insulated room with background noise at a minimum....
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This note was uploaded on 12/12/2011 for the course PHYS H90 taught by Professor Mcwilliams,r during the Fall '08 term at UC Irvine.

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Laquer+H90+Science+Paper+1+ - Alan Laquer 89863832 Physics...

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