Tuesday, September 14, 2010

And more!

Survey of College Students' MP3 Listening: Habits, Safety Issues, Attitudes and Education Alicia Hoover, Sridhar Krishnamurti. American Journal of Audiology (2010)
This piece was about a short survey of college students at San Diego State University. A third of the students surveyed reported using their MP3 players 5-7 days per week, and two-thirds reported they used them at least 3 days a week. Only half of the respondents reported their volume was set at or less than half. Nearly 20% and 25% reported listening to the MP3 players while riding in a car and on the bus (respectively). Over 90% of the students reported turning the volume up to overpower background noise, and more than a third reported sometimes listening to their MP3 players at full volume in certain situations.
Also, over half of the students expressed irritation with being advised to reduce their listening volume and less than half were aware of their ability to limit the maximum volume on their MP3 players. Nearly 70% of the students were willing to turn down the volume on their MP3 players to protect their hearing.
The authors concluded that, "There is a need for more organized public education on safety issues associated with MP3 player use," and I totally agree! Not only do we need to warn teenagers about the hazards of incredibly loud MP3 players, but also educate them about signs of hearing loss, and overexposure.


Stress Pathways in the Rat Cochlea and Potential for Protection from Acquired Deafness Richard A Altschuler, et. al. Audiology & Neuro-Otology (2002)
This article was another scientific one, so I didn't understand it as much as I would have liked, but the basic idea is a discussion of Hsp70, the heat shock protein induced by noise, hyperthermia, and ototoxic drugs. It is produced, "...in response to stress and provides for protection, recovery and repair..." but, "...there can be a delicate balance between protection/survival and cell death pathways..."
I guess it boils down to the idea that our bodies try to protect themselves but can go a little overboard.


Comparison of Audiometric Screening Criteria for the Identification of Noise-Induced Hearing Loss in Adolescents Deanna K Meinke & Noel Dice (2007)
This article addressed some interesting changes to the 'standard' school of thought regarding young adults and noise-induced hearing loss. In younger children (6-11 years old), only 8.5% had noise-induced threshold shift as opposed to the older children (12-19) who showed a NITS in 15.5% of children.
The authors mentioned two studies regarding the noise notch beginning at 6kHz instead of 4kHz: Salmivalli (1979), who found that the 6kHz notch appeared twice as often as the 4kHz notch, and Axelsson (1979) who found that, "earliest audiometric changes can often be found at 6000 Hz" before they generalize to 4kHz. Since we don't screen at 6kHz (or sometimes even 4kHz, for that matter), we don't typically notice.
The importance of screening adolescents comes from some frightening statistics, including, "...37% of children with mild sensorineural hearing loss failed at least one grade." For older students, the feeling of invincibility can result in failing to get help and therefore suffering in lectures. I know this because I have experienced it firsthand.
The authors also listed a couple ideas for 'fixing' the problem, including the possibility of using a video game to test the hearing of the students. "Perhaps," the authors wrote, "the game could be designed to educate the student about NIHL while screening for the disorder at the same time." Way to multitask! :) The other recommendation the authors included was standardizing the screening techniques used for early identification, something I feel is long overdue.

Susceptibility of the Noise-Toughened Auditory System to Noise-Induced Trauma Roger P Hamernik & William A Ahroon. Hearing Research (1999)
I never really thought about 'toughening' the auditory system but after I found the article I was incredibly intrigued. The idea that we could potentially toughen our ears to protect us during onslaughts of noise is encouraging. Unfortunately, the authors found that there may be a 'toughening' effect, but only because a permanent threshold shift means that the ear isn't receiving as much signal. There was no protective effect from the 'toughening' exposure.
There are three other similar articles which arrived at approximately the same conclusion, they are:
Conditioning the Auditory System With Continuous vs. Interrupted Noise of Equal Acoustic Energy: Is Either Exposure More Protective? Ruth A Skellett, et. al. Hearing Research (1998)
Noise-Induced Hearing Loss in the Noise-Toughened Auditory System. William A Ahroon & Roger P Hamernik. Hearing Research (1999)
Effect of an Initial Noise Induced Hearing Loss on Subsequent Noise Induced Hearing Loss. Ronen Perez, et. al. Hearing Research (2004)

Last, but not least...
Presbycusis, Sociocusis and Nosocusis. Karl D Kryter. Journal of the Acoustic Society of America (1983)
Through several population-based studies, this article explains the basics of presbycusis, sociocusis and nosocusis in our country. According to the article, presbycusis starts at age 20, possibly earlier. (My belief is that it is sociocusis at this age, not presbycusis.) Boys were found to have more prevalent/severe presbycusis than girls, presumably due to their preferred social habits (guns, trucks, etc.). The authors mention that, "Hearing sensitivity is increasing with maturation up to the age of roughly 16 years." and that sociocusis begins soon after that. So basically, the age at which teens are using their iPods the most is the age that sociocusis begins... Hmm...
The authors also explain the study of the Mabaan tribe in Sudan, which is hailed as a 'noise-free' population study. Unfortunately, there were inconsistencies with the method which call the results into question. If the error was in calibration, the results could still stand that there were no gender differences in hearing sensitivity, and that, "Presbycusis progresses at a slower rate in a noise-free society than it does in industrialized, relatively noisy societies." (Ultimately, this is sociocusis!)

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