Transcript Ear and voice part 2

Hearing Loss
Hearing loss can be divided into two basic types:
1. Temporary threshold shifts
2. Permanent loss
Hearing loss resulting from damage or aging of the central hearing mechanism
is permanent.
Certain types of outer or middle ear problems can be corrected, at least partially,
through surgery.
Permanent hearing loss can be caused by physical damage to the ear
mechanism, by disease, by drugs, or by natural aging process.
Prolonged exposure to loud sounds, particularly around 80 to 90 dB, can
produce temporary threshold shift.
Continued exposure to amplified rock music and other loud sounds has been
strongly implicated as a source of hearing damage.
Risk factors
Factors that may damage or lead to loss of the hairs and nerve cells in your inner ear
include:
Aging. The normal wear and tear from sounds over the years can damage the cells of
your inner ear.
Loud noises. Occupational noise, such as from farming, construction or factory work,
and recreational noise, such as from shooting firearms, snowmobiling, motorcycling, or
listening to loud music, can contribute to the damage inside your ear.
Heredity. Your genetic makeup may make you more susceptible to ear damage.
Some medications. Drugs such as the antibiotic gentamicin and certain chemotherapy
drugs can damage the inner ear. Temporary effects on your hearing — ringing in the ear
(tinnitus) or hearing loss — can occur if you take very high doses of aspirin or
nonsteroidal anti-inflammatory drugs (NSAIDs), antimalarial drugs or loop diuretics.
Some illnesses. Diseases or illnesses that result in high fever, such as meningitis, may
damage the cochlea.
http://www.howjsay.com/
Presbycusis
http://www.howjsay.com/
One form of hearing loss, presbycusis, comes on gradually as a person ages.
Presbycusis can occur because of changes in the inner ear, auditory nerve,
middle ear, or outer ear. Some of its causes are aging, loud noise, heredity, head
injury, infection, illness, certain prescription drugs, and circulation problems such
as high blood pressure.
Presbycusis commonly affects people over 50, many of whom are likely to lose
some hearing each year. Having presbycusis may make it hard for a person to
tolerate loud sounds or to hear what others are saying.
Tinnitus
Tinnitus, also common in older people, is the ringing, hissing, or roaring sound in
the ears frequently caused by exposure to loud noise or certain medicines.
Tinnitus is a symptom, not a disease, so it can accompany any type of hearing
loss.
Tinnitus can also be a sign of other important health problems, such as allergies
and problems in the heart and blood vessels. Tinnitus can come and go, or it can
persist or stop altogether.
http://nihseniorhealth.gov/hearingloss/hearinglossdefined/01.html
http://www.kidshealth.org/kid/health_problems/sight/hearing_impairment.html
Cochlear Implants
Cochlear Implants
Function
1. Microphone (a) picks up the sound and
sends it to speech processor (b or c), that
filters the sound into a series of frequency
bands.
2. The speech processor’s output is sent
to a small radio transmitter (d) that
broadcasts the signals to a receiverstimulator (e).
3. This electrical stimulus is sent to the electrodes (f) that are implanted along the
basilar membrane in the cochlea (g).
4. This artificial stimulation thus replaces the stimulation of the nerves in the
organ of Corti that would occur in the normal ear.
5. The implant uses 22 separate electrodes covering the frequency range:
below 100 Hz to above 6000 Hz.
6. The stimulation is then sent to the brain by the auditory nerve fibers (h).
Bernoulli’s Principle
Bernoulli’s principle is relevant to the operation of the vocal folds, as well as
the lips of a brass instrument player and the reed of a reed instrument.
The speed and pressure of air flow are related by an equation discovered
by Daniel Bernoulli (1700–1782).
The sum of the pressure plus the kinetic energy per unit volume of the
flowing air must remain constant.
1 2
P  dv  cons tan t.
2
Vocal Track
The source of sound for the human voice is the
vibration of the vocal folds, and the filter consists
of the resonant cavities forming the vocal track:
the larynx, the pharynx, the mouth, and the
nasal cavity.
Vocal Formants
What is the sound source for the vocal system?
Vibration of the vocal folds.
This vibration is brought about by a combination
of the force of the air from the lungs causing the
folds to open, followed by a Bernoulli force that
causes them to close.
http://www.youtube.com/watch?v=R7lhUUcWJNQ&feature=related
Frequency of oscillation of the vocal folds is determined primarily by the tension in the
vocal folds, which can be controlled.
Amplitude of the oscillation is affected by the rate of the airflow between the folds.
Frequencies of vocal fomants can be calculated using the length between the vocal
folds (closed end)) and lips (open end), 17-18 cm.