Parents of students need to purchase headphones. These are a compulsory item. KICE recommends students use volume restricted over-the-ear headphones. If you choose In-ear headphones you do so at your own risk even though students will be taken through a process to limit the volume. The volume for music can be limited on the iPad via Settings > Music > Volume Limit. (Step by step screenshots to come)
Most in-ear headphones easily allow levels up to and exceeding 100dB. Any noise intensity over 90 dB has specific time limits for exposure before irreversible damage is done to the cochlear. As a general guide, if you are using standard headphones/inserts and you cannot hear someone speaking at a normal conversational level (at a distance of about 1m) then the intensity level is usually above 90dB.
As children’s ear canals are different (smaller in size and are closer to the eardrum) the amount of amplification can be altered by up to 9 dB, raising the intensity of the sound from one similar to the noise output of a vacuum cleaner to that of a motorcycle engine. At these higher levels of exposure to noise damage can occur after only 15mins of exposure.
Most of the noise-restricted headphones limit the maximum intensity level to 89 dB, which is a safe level and can be used for an extended period. At this level kids can easily hear what is happening around them and also normal conversational levels with the headphones on their ears. These can be purchased at most electrical retailers for a reasonable price. The school will investigate an option where we may be able to sell them out of the bookroom.
Noise exposure is a function of loudness and time so if you wish to reduce your exposure you must firstly reduce the volume or loudness and then the time. Noise exposure is cumulative over your lifetime, meaning that every over exposure adds up – just like too much UV-radiation or exposure to the sun.
The national standard for noise exposure is 85 dB over an 8-hour period, but for every 3 dB increase in level, the resulting time of allowable exposure should be halved. For example at 88 dB the allowable exposure is cut to 4 hours; at 91 dB it is 2 hours; at 94 dB it is 1 hour and so on.
The Australian National Acoustic Laboratory, has several recent publications of research on their website to support the use of volume restricted devices in kids. http://www.nal.gov.au/index.shtml
The Music to my Ears Campaign provides practical hearing protection tips and to raise awareness about safe noise exposure levels. http://www.musictomyearscampaign.org/
The potentially damaging effects of excessive exposure to noise have been highlighted in Australian Hearing Binge Listening study. http://www.hearing.com.au/upload/binge-listening.pdf