In my office at the University of lighting consists of fluorescent tubes. A few months ago broke a and changed, so badly that buzzes a bit. When you're talking to alguine barely noticeable, but in silence is very disturbing. Sitting in the chair, if I move to the left or right increases or decreases the buzz almost canceled. Is that possible or is an illusion of some sort? I have no good pictures of the scene, but I have taken steps, and come to be those shown in the figure below. The fluorescent tube is about five feet above my head, right there is a wall a meter, and the maximum difference in sound (from maximum to minimum) occurs when I move horizontally about 30 cm. The latter is what it purports to represent in the scheme with two ears.
Suppose that the sound reaches my ears in two ways, first straight line, and another bouncing off the wall on the right. Then the two waves "interfere" in the point where they are maximum and minimum will be canceled, while where there are two peaks will be double the sound intensity. Just the topic of wave interference, as we cited in the previous entry (especially to illustrate that is not the same understanding that compute ).
I have fun in doing the exercise in trigonometry that calculating the paths of sound waves. The difference between the vertical path and bounced off the wall are 210 cm, while in the case of displaced orja 30 cm, the difference between direct and reflected path is 36.2 cm.
To finish we need to check the matter a fact, the frequency of tinnitus. The electric current to power the fluorescent, as any European power network, is alternating current at 50Hz. The sound is likely due to magnetizing current to any part that moves against another right at the same frequency, 50 Hz is also reasonable because it is an audible hum (the human ear from 20 to 20,000 Hz) quite serious. Almost all electrical appliances that make it hum at 50 Hz
If the sound is moving at 340 m / s in a cycle network (such that there are 50 in each second, which is what the 50-Hz) travel 340/50 = 6.8 m. So a full wave, one wavelength is 6.8 m. Between the maximum and zero crossing is a quarter wavelength, thus 170 cm.
do not know if my attempt to explain the thing saving drawings and formulas will have been even more confusing, but the end result is that it is consistent, that a shift in the ear of 30 cm is compatible with a range of 1 / 4 wavelength, a clearly audible difference.
Although everybody wave interference, a priori does not seem easy to find in everyday life, is that we find in the hum of electrical appliances when heard under certain conditions (not so rare).
0 comments:
Post a Comment