3.10.2 Physics of the Ear Flashcards
What is the basic purpose of the ear?
Used to transfer sound energy into electrical signals that are sent to the brain.
What happens in the outer ear?
External ear = funnels soundwaves and concentrates energy to smaller area.
Ear canal leads to eardrum - vibrates (sound waves = variations of air pressure)
Wax glands along canal keep it clean and lubricated.
What happens in middle ear?
Connected to the throat so equal atmospheric pressure both sides of eardrum.
3 tiny bones - transfer vibrations from ear drum, amplifying the forces.
What happens in inner ear?
Windows transmits vibrations to fluid in inner ear = pressure waves in fluid.
Nerve impulses sent via auditory nerve to the brain.
What is the intensity of a sound wave?
The amount of sound energy that passes, per second, per unit area.
(perpendicular to direction of the wave)
intensity = power / area
intensity is proportional to amplitude squared.
What is the range of hearring?
20Hz - 20000Hz
- most sensitive around 2-4 kHz (3 kHz = max. sensitivity)
What does perceived loudness depend on?
Intensity
Frequency
What is the threshold of hearing?
The minimum intensity of sound that can be heard by a normal ear at a freq. of 1kHz
What is dBA?
An adjusted decibel scale
- takes into account ear’s response to diff. frequencies.
- sounds of same intensity have same loudness for average human ear.
How is a loudness curve generated?
Signal generator at set intensity generates control freq. (1kHz)
Second signal generate at diff freq.
Play alternating sounds from each, alternating intensity on 2nd generator until sound appears to have same loudness.
What happens to hearing as age increases?
Hearing deteriorates - highest freq. affected most
What happens to ears damaged (by excessive noise)?
General hearing loss - around 4kHz affected most
What is needed for a person with hearing loss?
Higher intensities needed for same loudness
