I was talking to my friend Tim on the phone the other day and every few minutes he kept asking me to speak louder. The line was free, no cell phones were being used, I was talking just like now and we were both in the comfort of our homes. So it got me thinking, is it me or does he just not hear me? Well, the truth is that according to the National Institute on Deafness and other Communicative Disorders, over 30 million Americans are exposed to dangerous sounds on a daily basis. And that constant exposure is giving way to a serious health problem called noise-induced hearing loss. Today we will learn about the national health problem that is affecting nations, we will begin to understand how the ear works and how we as human beings hear, then we will break down sound in its relationship to hearing, trying to understand how loud is too loud. Loud music has long been attributed to noise-induced hearing loss, but until recently it was considered a health problem for adults and older adults. In the April 2005 edition of the journal Pediatrics, it is stated that approximately 12.5% ​​of children between the ages of 6 and 19 have noise-induced threshold shifts. Noise-induced threshold shifts can range from the need to turn up the stereo volume to the onset of NIHL. The article also mentions that the previously cited percentage is an increase of nearly 40% since 1985. Although the statistics are alarming, Americans are still unaware due to the lack of information about noise-induced hearing loss. Noise-induced hearing loss as documented at nidcd.nih.gov states that “noise-induced hearing loss can be caused by one-time exposure to a loud sound, as well as repeated exposure to sounds at various levels of volume over a long period of time". This means that just one time hearing something loud like an explosion, or years of listening to loud music, can have the same effect on our hearing. What is also alarming is that the symptoms of NIHL gradually increase over time, but I'll talk about that a little later. NIHL has several forms ranging from partial deafness, to tinnitus and total deafness. A person with partial deafness may never completely lose their hearing and is often helped greatly by the use of a hearing aid.