Bone conduction (Item No.: P )

Transcription

1 Teacher's/Lecturer's Sheet Bone conduction (Item No.: P ) Curricular Relevance Area of Expertise: Physik Education Level: Klasse 7-10 Topic: Akustik Subtopic: Schallerzeugung, - Ausbreitung und Wahrnehmung Experiment: Knochenleitung Difficulty Preparation Time Execution Time Recommended Group Size Easy 10 Minutes 10 Minutes 1 Student Additional Requirements: Experiment Variations: Keywords: Task and equipment Information for teachers Additional material In this ebperiment, the students can observe that sound can reach the inner ear not only via the outer and middle ear but also via the human bones. In medicine, bone conduction is used for diagnostic purposes. Based on the Rinne and Weber tests, which are used for medical diagnoses, the students will learn that bone conduction bypasses the sound conduction of the outer and middle ear. As a result, these ebperiments can be used to distinguish between sound conduction disorders (outer ear, middle ear) and sound sensation disorders (inner ear, auditory nerve). Prior to the ebecution of the ebperiment, the students should be familiar with the human ear. They should know that sound propagates not only in air, but in all kinds of media and, therefore, also in solid bodies. Notes concerning the evaluation of the experiment The ebperiments are not an instruction for self-diagnosis. They should merely demonstrate how a physician can narrow down the causes of auditory problems with the aid of the Rinne and Weber tests. lonclusive diagnoses are, of course, reserved for medical specialists, which is why the ebperiment results should not be used for the diagnosis of any kind of disorders. Please point this out to the students prior to the ebecution of the ebperiments.

2 Bone conduction (Item No.: P ) Task and equipment Task What is bone conduction and how do doctors make use of it? The human ear perceives sound in its environment usually through the air. The sound signals are processed in three different areas of the ear: in the outer ear (auricle and outer auditory canal), middle ear (eardrum, auditory ossicles, and auditory tube), and inner ear (cochlea and vestibular system). The actual auditory information is transmitted from the inner ear to the brain by the auditory nerve. This ebperiment ebamines the question as to whether sound can also be perceived in a different way than via the outer ear. 1. Ebamine the bone conduction of sound in the human body. 2. Find out what an ear, nose, and throat specialist understands by a Rinne test and a Weber test and what kind of information these tests can provide. Equipment Set-up and procedure Part 1: Bone conduction Position No. Material Order No. Quantity 1 Tuning fork 440 Hz Striking hammer

3 Fig. 1: A tuning fork is held against various different bones (here: collarbone) Strike the tuning fork with the striking hammer and hold it against various different bones of the body: forehead, jaw, breastbone, elbow, etc. Note down your observations in the report (under "Result - Observations 1"). Part 2: Rinne test Fig. 2: Rinne test: The tuneing fork is held against the bone behind the ear (picture on the left) and in front of the ear (picture on the right). Strike the tuning fork and hold its lower end against the bone behind the auricle (process of the temporal bone). Wait until the sound of the tuning fork can no longer be heard via this bone. Then, move the tuning fork in front of the auricle and observe whether the sound can still be heard in this position. Note down your observations (under "Result - Observations 2"). Part 3: Weber test

4 Fig. 3: Weber test: The tuning fork is held against the crown of the head. Strike the tuning fork and place it centrally on top of your head. Observe how you can hear the sound with both ears. Then, plug one ear with a finger and repeat the ebperiment. Note down your observations (under "Result - Observations 3").

5 Report: Bone conduction Result - Observations 1 (10 Punkte) Part 1: Bone conduction Describe how you can hear and feel the tuning fork when it is held against the various different bones. Result - Observations 2 (10 Punkte) Part 2: Rinne test Can you hear the sound of the tuning fork longer via the bone or via the open ear?

6 Result - Observations 3 (10 Punkte) Part 3: Weber test How do you hear the tuning fork when a) both of your ears are open: b) one ear is blocked: Evaluation - Question 1 (10 Punkte) Why can you hear the tuning fork when you hold it against a bone in the area of your chest or skull? In medical science, a distinction is made between auditory problems that are caused by sound conduction disorders and those that are caused by sound sensation disorders. Sound sensation takes place in the inner ear and in the nerve pathways to the brain, whereas sound conduction is the sound transport from the outer ear via the middle ear to the inner ear. Age-related hearing loss and acute hearing loss are sound sensation disorders, whereas an inflammation of the middle ear impairs the sound conduction.

7 Evaluation - Question 2 (10 Punkte) In healthy persons, sound is transported better through sound conduction in the outer and middle ear to the inner ear than via bone conduction. Based on this knowledge, how can you ebplain your observations during the Rinne test? Evaluation - Question 3 (10 Punkte) If the tuning fork can be heard longer through bone conduction than through the sound conduction of the ear during the Rinne test, what type of hearing disorder could this indicate a sound conduction disorder or a sound sensation disorder?

8 Evaluation - Question 4 (10 Punkte) The Rinne test cannot ebclude disorders concerning the sound sensation. This is why in the medical contebt, the Weber test is additionally used for diagnostic purposes. What would you ebpect if a Weber test (both ears open) is performed on a healthy person with intact sound sensation and conduction? Evaluation - Question 5 (10 Punkte) Sound is not only transported from the outer ear to the inner ear. In accordance with the theory of sound, the oscillation energy of the sound in the inner ear must also be carried off. Normally, this takes place via the middle ear and eardrum towards the outer ear. Why can you hear the sound of the tuning fork louder in the plugged ear during the Weber test with one plugged ear?

9 Evaluation - Question 6 (10 Punkte) During the Weber test, sound reaches the inner ear via bone conduction. If one of the ears is affected by a sound sensation disorder, will the sound of the tuning fork be heard louder or quieter in this ear? Evaluation - Question 7 (10 Punkte) What could one deduce from the Weber test if the sound of the tuning fork can be heard louder in the ear that is affected by a disorder?