Hearing Health 123

Life is defined in part as the ability to perceive external stimuli and respond to them. Besides vision, smell, and touch, hearing is a unique sense given to animals on Earth. Different animals produce and perceive different frequencies of sound waves. Dolphins can emit much higher frequency sounds than humans, known as "dolphin sounds." Bats can produce ultrasonic sounds beyond human hearing. Sound waves travel through air at approximately 340 meters per second, and the number of vibrations per second is called frequency, measured in Hertz (Hz). Physics teaches us that frequency multiplied by wavelength equals wave speed. Animals can adjust vocal cord tension to change sound frequency, producing resonance in the upper respiratory tract and creating loud sounds.

Humans can produce sounds between approximately 80–200 Hz, with men generally lower and women higher. Human hearing ranges from 20 to 20,000 Hz; frequencies above 20,000 Hz are considered ultrasonic. Dogs can hear up to 40,000 Hz, allowing them to detect subtle changes at night that humans cannot. The amplitude of a sound wave represents its energy, measured in decibels (dB). Normal speech is around 50 dB, while normal hearing thresholds are below 25 dB. Hearing thresholds of 25–40 dB indicate mild hearing loss, 41–70 dB moderate hearing loss, and 71–90 dB severe hearing loss, significantly affecting communication and social interaction.

The ear is divided into three parts: outer ear, middle ear, and inner ear. The inner ear connects to the brain via the auditory nerve. Any problem in these areas can lead to hearing loss.

Common Causes of Hearing Loss

The causes of hearing loss vary by population. Common reasons include:

1. Congenital Hearing Loss
   Hearing impairment in newborns is a common congenital defect. Approximately 1 in 500–1000 newborns has severe bilateral hearing loss, and 2–3 have mild to moderate or unilateral loss. Early detection and treatment within three months promote normal language development and benefit the child’s future.
2. Earwax Blockage, Middle Ear Effusion, or Chronic Otitis Media
   The outer ear canal is naturally structured to prevent water from entering. Earwax blockage, fluid in the middle ear, or chronic infections can impair hearing. Professional ENT consultation is recommended.
3. Noise-Induced
   Noise exposure at work is a major occupational hazard. Studies show workers in steel factories have significant hearing loss at 4kHz (29%) and 6kHz (31%). Loud entertainment venues also pose risks, with headphones, discos, KTV, rock concerts, and sporting events as common sources.
4. Age-Related
   After age 50, hearing begins to decline due to inner ear and auditory nerve degeneration, and reduced brain processing of language, leading to "can hear but cannot understand" situations.
5. Sudden Hearing Loss
   Sudden hearing loss in one ear may result from inner ear circulation issues or viral infections. Early medical attention is critical.
6. Ototoxic Medications
   Certain medications can damage the inner ear, including aminoglycoside antibiotics, furosemide, aspirin, some chemotherapy drugs (cisplatin), and heavy metals like mercury and lead.

How to Protect Your Hearing

1. Diet
   Patients with Meniere’s disease or inner ear fluid issues should maintain adequate sleep, avoid fatigue, eat a light diet, and avoid caffeine, highly sweet foods, and certain dairy or citrus products. Smoking and alcohol should also be avoided.
2. Medications
   Discuss alternatives with your physician if medications affect hearing.
3. Noise Protection
   Use earplugs in noisy workplaces and avoid loud entertainment venues.
4. Headphone Use
   In-ear headphones may cause damage due to sealing; over-ear headphones are safer. Follow the “60/60 rule”: listen at no more than 60% of maximum volume for 60 minutes daily, or 30 minutes as recommended in the U.S.

Treatment and Rehabilitation for Hearing Loss

1. Earwax Blockage, Middle Ear Effusion, or Chronic Otitis Media
   Treatable causes can be managed medically or surgically.
2. Otitis Media with Effusion
   Common in children, may require tympanostomy tubes if fluid persists over three months or affects hearing significantly.

Sudden Hearing Loss

Sudden loss in one ear may be caused by circulation problems, viral infections, diabetes, cardiovascular diseases, or radiotherapy for head/neck tumors. Early treatment with steroids or circulation-promoting therapy is most effective. About 60% of patients improve within the first week; after three months, recovery is limited.

Hearing Aids

Patients with 40–60 dB hearing loss have difficulty perceiving everyday sounds. Those with 60–90 dB loss rely on vision and touch. Complete hearing loss (>90 dB) makes daily life challenging. Hearing aids can improve communication. Studies show low adoption rates (39%), often due to cost or stigma. Medical guidance and support can help maximize hearing aid use and quality of life.