In this combined literature study and experiment, I investigated to what extent listening to loud music via headphones affected long term hearing loss. In spring of 2010, a group of college students at University of Virginia took a hearing test using a sound curve generating software. I compared the test results of students who were self-declared heavy users to those who were self-declared light users in conjunction with published standard values and found that on average, heavy headphone users' ears were 6.5% less sensitive than light headphone users'.
Invented in the early 1900's by Nathaniel Baldwin, headphones were meant for one purpose only: to convert sound clearly and efficiently from electrical signals to audible sound waves. Throughout its history, headphones have seen widespread usage all over the world, and thus have resulted in the formation of a multi-million dollar industry.
[...] In fact, a sound's decibel rating depends on two things: the loudness of a reference sound, which may be chosen arbitrarily, and the frequency of the reference sound. This method of measuring sound proved to be a bit cumbersome for certain individuals, and one day, someone invented the phon, denoted either as P or Lp, which is equivalent to 1 dB at 1 kHz (reference frequency), and with respect to the threshold of human hearing. For my experiment, I had my sound system play a reference tone at 40 phons. [...]
[...] A sound curve is a graphical representation of a subject's hearing abilities. Subjects listen to series of sounds played at different frequencies, and the sound, closest in loudness to a reference sound, that a subject can hear at a given frequency is plotted against the frequency to form a sound curve. See Appendix 1 for more detail on the importance of calibration and for a brief general background on the math of acoustics. I arbitrarily chose 6 months as the limit here to classify those [...]
[...] Results and Discussion: Literature Study In their study titled, “Effects of Listening to Music with Headphones on Hearing Especially under Noisy Conditions”, Doctors Miyake and Kumashiro found that subjects tended to increase headphone volume to cover up background noise, as expected. Sixty test subjects were divided into three groups: one that would listen to rock music, one that would listen to Japanese pop music, and one that would listen to traditional Japanese music. They were then taken to in seven different environments: a train, a bus, a tram, a subway, an underground subway station, a busy street, and a soundproof room. [...]
[...] Although this figure may seem small, the fact that these were students between 18 and 20 years old means that given a longer period of time, say or more years, these subjects' hearing abilities will be atrociously low. What was also a bit of a surprise was that the light group had, by no means, healthy ears. The graph shows a notable difference between the standard curve and light curve around the 60 Hz 1.5 kHz range. According to the graph, the light users' ears were less sensitive than the perfectly healthy ear. [...]
[...] The first explored to what extent would test subjects increase the volume of their listening device while wearing headphones in noisy locations, while the second looked into any immediate, short term hearing loss in subjects that would occur following periods of listening to loud music via headphones. In addition to these papers, I also looked at the OSHA safety regulations for safe headphone usage. All of the above information was readily available on the internet. Although the literature study was relatively straightforward, the experimental section was not. [...]
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