The Hearing Test part of this lab requires complete SILENCE.
Hearing Lab
Through the sense of hearing we are placed into direct, intimate contact with the surrounding world. Musical, vocal, and other sonic impressions flood us constantly. The normal human ear is sensitive to sonic frequencies ranging from about 20 to 20,000 Hertz (1 Hz = 1 cycle/second), although the range varies with age and other individual factors. Several mammalian species, including bats, dolphins and whales, and many rodents, can detect much higher frequencies - Ultrasound. Elephants, on the other hand, detect lower frequencies - Infrasound. Sensitivity of the human ear varies with the sonic frequency. Hearing in humans is most sensitive in the range 500-4000 Hz.
How our Ears hear:
The conduction of sound through the middle ear is facilitated by the action of the three smallest bones in the human body, the auditory ossicles. The outermost bone, the malleus (hammer), is secured to the inner aspect of the eardrum itself. The innermost bone, the stapes (stirrup), is positioned with its foot plate in the oval window of the cochlea. The incus (anvil) connects the two. These three bones respond to sounds coming to the eardrum from the surrounding world and transmit the delicate vibrations to the fluid within the cochlea. This aspect of the hearing process is ordinarily referred to as the conductive phase.
Sound can also be transmitted to the fluid of the cochlea by direct conduction through the bones of the skull, by a process in which no vibrations pass through the auditory ossicles. This kind of direct bone conduction provides an alternative pathway for sound transmission in individuals with middle-ear defects. To some extent you hear the sound of your own voice through the mechanism of direct bone conduction.
Two Types of Hearing Loss:
Conductive hearing loss occurs when sound is not conducted efficiently through the outer ear canal to the eardrum and the tiny bones (ossicles) of the middle ear. Conductive hearing loss usually involves a reduction in sound level or the ability to hear faint sounds. This type of hearing loss can often be corrected medically or surgically. Some possible causes of conductive hearing loss: Fluid in the middle ear from colds, Ear infection (otitis media), Allergies, Poor eustachian tube function, Perforated eardrum, Benign tumors, Impacted earwax, Presence of a foreign body, Absence or malformation of the outer ear, ear canal, or middle ear.
Sensorineural hearing loss (SNHL) occurs when there is damage to the inner ear (cochlea), or to the nerve pathways from the inner ear to the brain. Most of the time, SNHL cannot be medically or surgically corrected. This is the most common type of permanent hearing loss. SNHL reduces the ability to hear faint sounds. Even when speech is loud enough to hear, it may still be unclear or sound muffled. Some possible causes of SNHL: Illnesses, Drugs that are toxic to hearing, Hearing loss that runs in the family (genetic or hereditary), Aging, Head trauma, Malformation of the inner ear and Exposure to loud noise.
Weber Hearing Test
In the Weber test a vibrating tuning fork (256 Hz) is placed in the middle of the forehead, above the upper lip under the nose over the teeth, or on top of the head equal distance from the patient's ears on top of thin skin in contact with the bone. The patient is asked to report in which ear the sound is heard louder. A normal weber test has a patient reporting the sound heard equally in both sides. In an affected patient, if the defective ear hears the Weber tuning fork louder, the finding indicates a conductive hearing loss in the defective ear. In an affected patient, if the normal ear hears the tuning fork sound better, there is sensorineural hearing loss on the other (defective) ear. In the case where the patient is unaware or has acclimated to their hearing loss, the clinician has to use the Rinne test in conjunction with the Weber to characterize and localize any deficits. That is, an abnormal Weber test is only able to tell the clinician that there is a conductive loss in the ear which hears better or that there is a sensorineural loss in the ear which does not hear as well.
The Rinne Test:
The Rinne test, originally designed by the German otologist, Dr. A. Rinne, differentiates between conductive and sensorineural hearing impairments, and is an important aspect of auditory diagnosis. A vibrating tuning fork is held against the mastoid process of the temporal bone (the knob at the base of the ear) until the subject can no longer hear the tone, at which time the investigator quickly places the fork in front of the ear.
Someone with normal hearing can still hear the tone for a short time by direct air conduction and is said to be Rinne positive. Individuals with middle-ear defects usually are Rinne negative; that is, they hear better with temporal bone conduction than with conduction through the middle ear. Individuals with sensorineural defects (defects of the sensory mechanism in the cochlea itself, defects in the cranial nerve VIII, or central nervous system damage) are Rinne positive; that is, they can hear much better on a relative basis through air conduction than through bone. Normal hearing is when the sound of the tuning fork is heard with equal loudness through bone conduction and air conduction.
PRE-LAB QUESTIONS:
1. What is the normal hearing range?
2. What is Ultrasound? What is Infrasound?
3. Which animals hear at higher frequencies than humans?
4. Which animals hear at lower frequencies than humans?
5. Name the 3 auditory ossicles. What is their basic function?
6. What is Conductive Hearing Loss? Is it treatable? How is it caused?
7. What is Sensorineural Hearing loss. Is it treatable? How is it caused?
8. What is the Rinne Test?
Materials: tuning fork – 512Hz, sterile cotton, A VERY QUIET ENVIRONMENT
Procedures : Both ears should to be evaluated with several tuning forks of different frequencies. Be sure to enter your results in the data sheet!
First: Conduct the Weber Test 256Hz
Do you know if you have hearing loss? ______If yes, which ear? ______
Do you have a cold right now? ______
After conducting the test, Can you hear the tuning fork sound equally in both ears? Yes No
Hearing Loss detected? Yes or No
Affect Ear ______
Second: Conduct the Rinne Test: 512 HZ
1. Students should work in pairs for this test; one as subject (listens to vibrations), the second as investigator (uses tuning fork).
a. The investigator lightly strikes the tuning fork with a soft mallet (or their palm), and presses it to the mastoid process of the subject. (bone right behind the ear)
b. As soon as the subject reports they can no longer detect the sound, the investigator positions the fork in front of the external ear. A Rinne Positive test is when the sound heard outside of the ear is louder than that heard of the initial sound heard when the tuning fork end was placed against the skin on top of the mastoid process behind the ear. If the sound is louder when the tuning fork is placed on the skin (bone conduction) than air conduction (placed by the ear), the person is Rinne negative.
2. The test should also be conducted in the reverse manner; that is, air conduction followed by bone conduction, to verify the conclusions.
3. Repeat these steps with just one ear, but this time, simulate conduction deafness by putting a small piece of cotton in the ear you are testing.
Results: Complete the blank with a YES or NO
Rinne Test Right Ear
A. Could you hear the tuning fork first at the Mastoid _____ and then louder at the Ear ______
B. Could you hear the tuning fork first at the Ear _____ and then at the louder Mastoid ______
Rinne: positive or negative or normal
Left Ear
A. Could you hear the tuning fork first at the Mastoid ____ and then louder at the Ear ______
B. Could you hear the tuning fork first at the Ear ______and then louder at the Mastoid ______
Rinne positive or negative or normal
Right Ear with Cotton
A. Could you hear the tuning fork first at the Mastoid ____ and then at the Ear ______
B. Could you hear the tuning fork first at the Ear ______and then at the Mastoid ______
Rinne positive or negative
BALANCE (EQUILIBRIUM)
We all are aware that in sitting, reclining, or standing erect we have a very particular sense of being in a state of balance. Without this sense we would be unable to maintain a fully alert conscious life, as anyone knows who has experienced disequilibrium or vertigo. The sense of balance or equilibrium is dependent upon the proper functioning of an organ of the inner ear, the semicircular canals, but is also associated with sight, hearing, and the proprioceptive sense (the awareness we have of our body movements and of where our limbs are located in space).
Procedures
Students will work in groups of three for this experiment.
1. Use on of the flooring tiles to roughly outline of the subject's foot.
2. The subject should stand in the tile with one foot and touch the other foot to their knee in any way they choose.
3. The test will measure the length of time the subject can remain standing in this position (with one foot within the drawn outline and the other foot touching the knee) to a limit of 90 seconds. One student will act as timer; the second will observe the movements of the subject and call out the moment when the trial is terminated.
4. With the procedure outlined above, test the ability of the subject to balance themselves under four separate conditions.
a. With eyes open and ears unplugged.
b. With eyes blindfolded and ears unplugged.
c. With eyes open and ears plugged.
d. With eyes blindfolded and ears plugged.
5. Rotate the subject, timer, and referee after each trial to minimize the effects of fatigue.
6. Record your data and collect the group data for analysis.
BALANCE RESULTS: TIME IN SECONDS
YOUR DATA
With eyes open and ears unplugged. ______
With eyes blindfolded and ears unplugged.______
With eyes open and ears plugged. ______
With eyes blindfolded and ears plugged.______
PARTNER #1 DATA
With eyes open and ears unplugged. ______
With eyes blindfolded and ears unplugged.______
With eyes open and ears plugged. ______
With eyes blindfolded and ears plugged.______
PARTNER #2 DATA
With eyes open and ears unplugged. ______
With eyes blindfolded and ears unplugged.______
With eyes open and ears plugged. ______
With eyes blindfolded and ears plugged.______
GROUP DATA: TIME IN SECONDS
NAMES OFSTUDENTS / AVG
eyes open and ears unplugged
eyes blindfolded and ears unplugged
eyes open and ears plugged
eyes blindfolded and ears plugged
Create a Bar Graph of the GROUP averages. Label X and Y axis
Title: ______
What conclusions can you draw concerning the roles of hearing and sight with balance? Are they equally important or is one “more” important. Use the lab results to back your statement up!
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