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 * 16. Explain that sound is produced by vibrating objects and that the frequency of the sound is the same as the frequency of the vibration of the source of the sound**

Sound is a form of energy that is caused by a vibrating object. These vibrations set up vibrations of the same frequency in the medium through which the sound is passing. The vibrations in the medium are detected by a structure such as the ear and converted into the sensation of sound. For example a source vibration of 100 Hz tarvels through air particles at 100 Hz before arriving at the human ear at 100 Hz. The human ear then vibrates. Thus an initial sound source with a frequency will arrive at the human ear at the same frequency.

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This video explains the sound production through the vibration of an object and its relationship to the frequency emitted through a medium over a distance.


 * 17. Outline the structure of the human larynx and the associated structures that assist the production of sound**

The larynx is a sophisticated structure situated in the throat-neck region in front of the fourth, fifth, and sixth cervical vertebrae. It is part of the trachea, the passage surrounded by rings of cartilage that leads from the oral activity to the lungs and the bronchi. The function of the larynx is to produce sound. The larynx consists of nine different cartilages. The vocal cords are connected through some of these cartilages and the vocal cords spread across the tracheal opening. They are made of elastic fibres. As air comes upwards from the lungs, the vocal cords vibrate creating sound. The vocal cords and the entire larynx surround a narrow opening in the trachea called the glottis. Speech involves the passage of air through the glottis and the vocal cords vibrate as the air passes through it. The pitch of the sound is affected by the distance and pressure of the vocal chord as well as the diameter of th glottis. Loudness is affected by the intensity of air vibrating the vocal cords.

This is a front view of the larynx. It details the main structures providing a visual image of how it looks and situated inside humans.

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Expresses the parts of the larynx and the relation to the openng of the glottis.


 * 18. Outline and compare the detection of vibrations by insects, fish and mammals**

An animal that has a receptor to detect vibrations, can 'hear' incoming sound and use it to gather information about the surrounding environment. In mammals, the ear has 3 main sections. The external ear collects the vibration, the middle ear transmits the vibration and the inner ear contains the main hearing organ, cochlea. Thecochlea contains organ of Corti, which has tiny hairs that receive the vibrations and convert them into electrical impulses so they can be sent to the brain via a series of nerve cells.

As sound travels faster in water than air, fish have ears on the inside of the body. The sound passes easily through the body to 2 internal ears that are filled with fluid and lined with cilia. The cilia detect the fluid movement caused by transmitted vibrations. Some fish detect sound with their swim bladders, which are filled with air and easily compressed. Once the swim bladder has detected the sound, it sends the signal on to the ear where the hair cells detect it and send it to the brain for interpretation. As fish move through the water they use neuromasts to detect movement. The neuromasts have hair cells like the inner ear and detect sounds. Some fish have lateral line systems, which are a series of small canals near the head and sides of the body that contain the neuromasts.

Insects can detect sounds in a variety of ways and a very high frequencies. Moths, cicadas and grasshoppers have tympanic membranes on their abdomen while grasshoppers have them on their legs. These membranes are where the sound energy is transferred into an electrical impulse and sent to the brain via nerves. More examples include mosquitoes having hairs on their antennae, which detect minute vibrations in the air. Bees, ants and termites have mechanoreceptors on their legs, which they use to detect sound travelling through the ground.

pinna tympanic membrane ear ossicles oval window round window cochlea organ of Corti auditory nerve**
 * 19. Describe the anatomy and function of the human ear, including:

The human ear consists of the three regions of the outer ear, middle ear and inner ear. The outer ear has the pinna leading into the external auditory canal. Glands lining the canal produce a wax that traps invading bodies. On the inside surface of the outer ear is the tympanic membrane or eardrum. It separates the outer ear from the middle ear. The middle ear has three small delicate bones called ossicles. They are the malleus, the incus, and the stapes. The middle ear opens into the Eustachian tube, which leads to the pharynx and equalises the pressure on either side of the eardrum. The oval window inside the stapes, is a membrane covering an opening into the inner ear and marks the border between the middle and inner ear. The lower round window is a membrane stretching across an opening, adjoining the cochlea in the inner ear. The cochlea in the inner ear is involved in hearing. The cochlea contains three parallel chambers, with vestibular canal at top, tympanic canal below and in the middle cochlear duct. The cochlear duct contains the organ of Corti for receptor cells for sound. These are hair cells and synapse onto sensory neurons. The auditory nerve collects these sensory neurons and sends them to the brain.

The human ear functions when sounds are emitted, they cause the air to vibrate. The vibrating air travels through the outer ear and strikes the eardrum(tympanic membrane). The eardrum vibrates, transfers the sound energy to the ossicles and they start vibrating. These vibrations are transferred to the fluids in the inner ear. When the fluids press against membranes in the inner ear, they cause forces to be exerted on the small hair cells in the organ of Corti. This activates adjacent neurons that send messages to the brain. The brain interprets these messages as sound.



This diagram above represents all parts of the human ear providing a visual basis and where they are located.

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This provides a clear basis for the anatomy and function of the human ear as it explains the process of hearing thus showing how all parts of the ear work as well as its purpose for sound.


 * 20. Outline the role of the Eustachian tube**

Consisting of an osseous and cartilagineous section, the Eustachian tube is 3 to 4 cm long. The middle ear opens into the Eustachian tube, which leads to the pharynx (back of the mouth or throat region) and equalises the pressure on either side of the eardrum (between the middle ear and the atmosphere). The Eustachian tube is normally closed and flattened but swallowing and yawning opens it for sufficient time to equalise the pressure between the middle ear and the external environment. The eustachian tube has three functions: ventilation, drainage, and protection. When the eustachian tube is open it allows ventilation of the middle ear and balancing of middle ear and atmospheric intensity. The middle ear then clears unwanted waste. Through being obstructed physiologically, the Eustachian tube protects the middle ear from secretions and sound.

The diagram shows the Esustachian tube and its connection to the rest of the ear, providing a visual insight into its role.