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A hearing impairment or deafness is a full or partial decrease in the ability to detect or understand sounds. Caused by a wide range of biological and environmental factors, loss of hearing can happen to any organism that perceives sound. “Hearing impaired” is often used to refer to those who are deaf, although the term is no longer politically correct. In Deaf culture, they prefer the terms Deaf and Hard of Hearing.

Sound waves vary in amplitude and in frequency. Amplitude is the sound wave’s peak pressure variation. Frequency is the number of cycles per second of a sinusoidal component of a sound wave. Loss of the ability to detect some frequencies, or to detect low-amplitude sounds that an organism naturally detects, is a hearing impairment.

The severity of hearing loss is measured by the degree of loudness, as measured in decibels, a sound must attain before being detected by an individual. Hearing loss may be ranked as mild, moderate, severe or profound. It is quite common for someone to have more than one degree of hearing loss (i.e. mild sloping to severe). The following list shows the rankings and their corresponding decibel ranges:

• Mild:
  • for adults: between 25 and 40 dB
  • for children: between 20 and 40 dB
• Moderate: between 41 and 55 dB
• Moderately severe: between 56 and 70 dB
• Severe: between 71 and 90 dB
• Profound: 90 dB or greater

The quietest sound one can hear at different frequencies is plotted on an audiogram to reflect one’s ability to hear at different frequencies. The range of normal human hearing (from the softest audible sound to the loudest comfortable sound) is so great that the audiogram must be plotted using a logarithmic scale. This large normal range, and the different amounts of hearing loss at different frequencies, make it virtually impossible to accurately describe the amount of hearing loss in simple terms such as percentages or the rankings above.

Measuring hearing loss in terms of a percentage is debatable in terms of effectiveness, and has been compared to measuring weight in inches. Though in specific legal situations, where decibels of loss are converted via a recognized legal formula, one can infer a standardized “percentage of hearing loss” which is suitable for legal purposes only.

Another method for determining hearing loss, is the Hearing in Noise Test (HINT). HINT technology was developed by the House Ear Institute, and is intended to measure an ability to understand speech in quiet and noisy environments. Unlike pure-tone tests, where only one ear is tested at a time, HINT evaluates hearing using both ears simultaneously (binaural), as binaural hearing is essential for communication in noisy environments, and for sound localization.

This Article is Taken from: http://en.wikipedia.org/wiki/Hearing_impairment

Final Exam for ENT265:

Date: 30 April 2009

Place: DKG5

Good Luck!

YOUR LIGHT SWITCH IS YOUR VOTE

This year, Earth Hour has been transformed into the world’s first global election, between Earth and global warming.

For the first time in history, people of all ages, nationalities, race and background have the opportunity to use their light switch as their vote – Switching off your lights is a vote for Earth, or leaving them on is a vote for global warming. WWF are urging the world to VOTE EARTH and reach the target of 1 billion votes, which will be presented to world leaders at the Global Climate Change Conference in Copenhagen 2009.

This meeting will determine official government policies to take action against global warming, which will replace the Kyoto Protocol. It is the chance for the people of the world to make their voice heard.

Earth Hour began in Sydney in 2007, when 2.2 million homes and businesses switched off their lights for one hour. In 2008 the message had grown into a global sustainability movement, with 50 million people switching off their lights. Global landmarks such as the Golden Gate Bridge in San Francisco, Rome’s Colosseum, the Sydney Opera House and the Coca Cola billboard in Times Square all stood in darkness.

In 2009, Earth Hour is being taken to the next level, with the goal of 1 billion people switching off their lights as part of a global vote. Unlike any election in history, it is not about what country you’re from, but instead, what planet you’re from. VOTE EARTH is a global call to action for every individual, every business, and every community. A call to stand up and take control over the future of our planet. Over 74 countries and territories have pledged their support to VOTE EARTH during Earth Hour 2009, and this number is growing everyday.

We all have a vote, and every single vote counts. Together we can take control of the future of our planet, for future generations.

VOTE EARTH by simply switching off your lights for one hour, and join the world for Earth Hour.

Saturday, MARCH 28 from 8.30PM to 9.30PM!

Reference web: http://www.earthhour.org

Rechargeable LED Torch is a DIY pocket size LED torch light using single AA rechargeable battery, super bright white LED and rechargeable using standard USB port. This is a great DIY project where you can learn about voltage booster and USB charger for AA rechargeable battery.

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