Sensitivity Of The Human Ear Cochlea Biology Essay

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Witnessing many hearing aid dependant people across the world has lead to a drive in acquiring what variables influence the functioning of the human ear.

Hearing occurs by the detection of the sound pressure waves by the pinna and these are further transformed into an array of nerve impulses in the middle ear which are interpreted by the brain. Human ear can differentiate between the pitch, tone, quality and loudness of music and speech.

Ageing affects all body functions but is it gender biased? Observing how age and gender affect the ear function could determine why ear deterioration, temporary and permanent hearing loss occur. As distance increases hearing decreases. How age, gender and quality of sound affect hearing could help in further development of sound technology, new hearing aids and methods of surgery into repairing any damage. A suitable process to measure all these variables can be ethically designed and carried out on a number of Subjects.

It is observed that with increasing distance and age, the loudness of sound must be increased and the efficiency of the ear reduces; more for men than women.

This investigation has only brought about a way forward for aiding the middle ear. No internal observations were made as ethically only external observations could be completed. A medical license would be required for any internal interventions. A limitation of this investigation is that the results obtained are purely observer based.

A sense of achievement was felt at my age because the research leads to an understanding of the human ear and factors affecting its functioning. An exposure to the scientific method of discovery where observations made, hypothesis proposed, experiment and data collection done and conclusions drawn. This enhanced scientific temper will help me for further research works in the medical field at university.

Word Count: 299

Table of Contents

Approach:

An experimental approach is taken where tests will be carried out on subjects with respect to age, gender and loudness of sound to witness their impact on the functioning of the human ear cochlea.

The data collected will be analysed to evaluate the factors affecting the functioning of it.

The three variables being investigated for their influence on its functioning have been chosen after detailed research and real life experiences where these variables seem to play a key role in its functioning according to the "Subject" being observed.

Approaching this investigation with the aim to discovering whether age, gender and the loudness of sound can affect one of the major sense organs could be key to further advancing hearing technology, could give more in depth knowledge of the human ear system and the impact of genetic factors along with the surrounding environment on its functioning. Observing each variable and their influence on the ear, new solutions for improving hearing with age according to gender could be discovered and further developed.

Introduction:

Base Knowledge:

The human ear is an important sense organ which detects sound. In the ear, the sound pressure waves travel through the ear and are later converted into an array of nerve impulses which are sent to the brain. The outer part of the ear known as the pinna collects the sounds which pass into the ear as pressure waves, amplifies these waves through the middle section of the ear and is passed into a liquid medium from a medium of air. The hollow channels found in the inner ear contain liquid along with a sensory epithelium which is covered with hair cells, these hair cells are mechanoreceptors which, when stimulated, release a chemical neurotransmitter. These sound pressure waves are directed into the external auditory canal which is approximately '26 mm long and 7 mm' [1] in diameter. The external auditory canal is closed at one end by the ear-drum (tympanic membrane). This consists of a combination of radial and concentric fibres which vibrate with small amplitude.

COCHLEA[Figure 1 Diagram showing the Structure of the Human Ear]http://www.hearingprofessionals.co.nz/Images/The-Human-Ear.gif

To prevent the reflection of sound energy between the middle ear and inner ear, the air density of the middle ear and the fluid density of the inner ear have to be matched as they are different. The opposition of an elastic medium to the passage of sound waves through it is known as the acoustic impedance. This is directly proportional to the density of the medium. As the air-fluid density differs, the acoustic impedance between the middle ear and inner ear must be matched to avoid the loss of sound energy by reflection. This type of matching is achieved by three ways. One being that the round window (fenestra rotunda), has the function of acting like a pressure releasing valve by the bulk movement of the inner ear fluid when a high enough pressure is exerted on it. This in-turn reduces the effective impedance of the fluid to a value closer to air. The next way being the ossicle lever system, this acts as a force magnifier. This works by applying the same mechanical advantage of the lever system to the magnification of the force on the ear-drum being applied on the oval window. Due to the area of the ear-drum being about 20 times bigger than the cross-sectional area of the oval window, the pressure across the oval window will be amplified as the high pressure can put the denser inner ear fluid into motion.

The ear cochlea is a very delicate organ in the hearing process which contains many complex structures. This organ detects vibrations which enter the ear, it is a spirally coiled and fluid-filled tube. 'The cochlea is filled with a watery liquid, which moves in response to the vibrations coming from the middle ear via the oval window. As the fluid moves, thousands of "hair cells" are set in motion, and convert that motion to electrical signals that are communicated via neurotransmitters to many thousands of nerve cells. These primary auditory neurons transform the signals into electrical impulses known as action potential, which travel along the auditory nerve to structures in the brainstem for further processing.' [2] The sound waves which are moving through the fluid push against the hair cells and with enough pressure make them bend, eventually causing them to fire which transforms the waves into nerve impulses which are then-on sent to the brain. It is protected by the middle ear from sudden increases in pressure intensities which may travel through the eustachian tube when it opens for swallowing, yawning or chewing. This tube usually remains shut to help equalize the air pressure on each side of the ear-drum. By doing this, the ear drum vibrates efficiently and stops the ear-drum and cochlea from rupturing due to the sudden change in pressure.

'Audition is the scientific name for the sense of sound. Sound is a form of energy that moves through air, water, and other matter, in waves of pressure. Sound is the means of auditory communication, including frog calls, bird songs and spoken language. Although the ear is the vertebrate sense organ that recognizes sound, it is the brain and central nervous system that "hears". Sound waves are perceived by the brain through the firing of nerve cells in the auditory portion of the central nervous system. The ear changes sound pressure waves from the outside world into a signal of nerve impulses sent to the brain.' [3] The ability to discriminate the differing frequencies in the sound waves which enter the ear is controlled by the ear cochlea. The average range of audible frequency for the human ear is between '20 Hz and 20 kHz' [4], the upper limit decreases with age. Sound waves below 20 Hz are known as subsonic, here the sound waves barely move the perilymph fluid in the helicotrema, the basilar membrane and the fibres of the Corti are not disturbed. Oppositely, sound waves above 20 kHz are called ultrasonic.

The tolerance to the varying sound frequencies, response time to vibrations, condition of the hair cells, speed of electrical signals and overall functioning of the ear cochlea varies from person to person according to age and gender. When sound is directed into the ear, it has a bigger impact on the working of your inner ear. Listening to lower volumes for longer periods of time can have the same level of damage as listening to higher volumes for short periods of times. Factors increasing the possibility of cochlea damage include gender, increasing of age, genetic factors, general noise tolerance, loudness and intensity of sound.

http://www.kingswaybaptist.co.za/Portals/6/images/The%20Wonder%20Of%20Man/Ear/Ear04.jpg

[Figure 2 Graph showing the pain thresholds for the human ear in relation to sound energy, sound pressure and frequency of sound]

The loudness of a sound is subjective and is determined by its intensity, frequency and the listener's response. It is the measure of power carried in a longitudinal sound wave whereas pitch is a measure of frequency. It takes into account the measure of the ear's response to the sound's intensity, however it does not take into the account the hearing level of the listener or the response their ear has to differing frequencies. This is why any equal change in the sound intensity is not perceived as an equal change in the loudness. Sound intensity is a measurable quantity and is the amount of energy that a sound wave brings to a unit area per second.http://www.antonine-education.co.uk/Physics_A2/Options/Module_6/Topic_3/graph_3.gif

[Figure 3 Graph showing Sound Intensity against Frequency]

Table of sound levels L (loudness) and

corresponding sound pressure and sound intensity

Sound Sources

Examples with distance

Sound Pressure

Level Lp dBSPL

Sound Pressure p 

N/m2 = Pa

Sound Intensity I 

W/m2

Jet aircraft, 50 m away

140

200

100

Threshold of pain

130

63.2

10

Threshold of discomfort

120

20

1

Chainsaw, 1 m distance

110

6.3

0.1

Disco, 1 m from speaker

100

2

0.01

Diesel truck, 10 m away

  90

0.63

0.001

Kerbside of busy road, 5 m

  80

0.2

0.0001

Vacuum cleaner, distance 1 m

  70

0.063

0.00001

Conversational speech, 1 m

  60

0.02

0.000001

Average home

  50

0.0063

0.0000001

Quiet library

  40

0.002

0.00000001

Quiet bedroom at night

  30

0.00063

0.000000001

Background in TV studio

  20

0.0002

0.0000000001

Rustling leaves in the distance

  10

0.000063

0.00000000001

Threshold of hearing

    0

0.00002

0.000000000001

Sound intensity levels are measured on a decibel scale (dB) which is logarithmic, a sound level meter can be used to calculate an accurate reading. 'Sound Level meters measure sound pressure level and are commonly used in noise pollution studies for the quantification of almost any noise, but especially for industrial, environmental and aircraft noise.'[5] 'They have a pointy stick at the top, which is the microphone that samples and measures the sound. The stick keeps the microphone away from the body of the instrument, cutting out reflections, and giving a more accurate measurement. Inside the square box at the bottom of the meter, electronic circuits measure the sound detected by the microphone and amplify and filter it in various ways before showing a readout on a digital LCD display.'[6]

[Figure 4 Table showing various sound levels with their relative sound pressure levels and sound intensity levels]

'Age-related hearing loss is called presbycusis. As some people age, structures of the ear become less elastic and undergo other changes that make them less able to respond to sound waves, contributing to hearing loss. In many people, exposure to noise over many years worsens the changes caused by aging. Age -related hearing loss begins early, starting some time after age 20. However, it progresses very slowly, and most people do not notice any changes until well after age 50.' [7] 'In otosclerosis, a hereditary disorder, the bone surrounding the middle and inner ear grows excessively. This exuberant growth immobilizes the stirrup (the ear bone attached to the inner ear) so that it cannot transmit sounds properly. Otosclerosis tends to run in families and may develop in someone who had measles as a child. Hearing loss first becomes evident in late adolescence or early adulthood. About 10% of adults have some evidence of otosclerosis, but only about 1% develops hearing loss as a result.' [8]

"There are three main types of hearing loss which can cause a profound hearing loss in a patient - conductive, sensory and neural." Conductive hearing loss is caused by an abnormality in the outer and/or inner ears causing the sound energy not being conducted to the inner ear and further on the brain. http://www.osha.gov/dts/osta/otm/noise/images/conductive_loss_audiogram.gif

[Figure 5 An audiogram showing the hearing level against frequency of conductive hearing loss]

A sensory hearing loss occurs when there is damage to the inner ear with or without damage to the outer and/or middle ear. Most cases of this type of hearing loss are due to hereditary factors or congenital nature along with the possibility of a post-birth acquired sensory hearing loss. Most cases are irreversible through surgical implication with the only other solution being a cochlear implant. http://www.osha.gov/dts/osta/otm/noise/images/sensorineural_loss_audiogram.gif

[Figure 6 An audiogram showing the hearing level against frequency of sensorineural hearing loss]

A neural hearing loss is when the outer, middle and inner ear function normally but a growth of tissue or any abnormalities are seen on the auditory nerves. Due to this patients can suffer from hearing loss to one ear, tinnitus (ringing in the ear) and balance problems. Apart from the degree of hearing loss, the range of audible sounds is also affected; this selective frequency loss can also limit speech discrimination. For patients with hearing loss, there are established ranges of sound intensity level for the different types of hearing loss which are shown in their respective frequency intervals, as shown in Figure 7 below.

http://www.nonoise.org/hearing/hcp/54.gif

[Figure 7 showing the established hearing loss frequencies and threshold levels for the human ear]

The ranges of normal hearing and hearing loss range from 10 dB to 91 dB. 10 dB to 20 dB is the range for normal hearing, 21 dB o 45 dB is the range for mild hearing loss where the patient would have difficulties hearing normal conversations, soft speech, some consonant sounds (see figure 8 below) and under noisy conditions experience difficulty hearing sounds.http://www.hdhearing.com/images/gifs/audiospeech.gif

[Figure 8 a graph showing the threshold level and audible frequency level and the letters of the alphabet]

This type of hearing loss does not require a hearing aid but further protection of ears from loud noise would be advised. 46 dB to 60 dB is the range for moderate hearing loss, with this the patient would experience more difficulty hearing conversation, loudness of speech will be lost and misinterpretation of consonant sounds will occur. A hearing aid could provide support if speech discrimination is good and any background noise is kept to a minimum. 61 dB to 75 dB is the range for moderately severe hearing loss, this is common among the elderly due to the effects aging has on the inner ear. Distinguishing between words and higher frequency sounds is hard as both ears will be affected. A hearing aid can provide support to amplify any soft sounds and leave any low frequencies unchanged. 76 dB to 90 dB is the range for severe hearing loss, any normal conversations will become inaudible for the patient. A hearing aid can only provide minimal help in distinguishing sounds and conversations, the patient is most likely to lip read. 91 dB is the range for profound hearing loss, which could be conductive, sensory or neural a hearing aid is highly unlikely to support the patient.

These hearing problems can be treated by a number of methods such as hearing aids and cochlea implants. 'Sound amplification with a hearing aid helps people who have either conductive or sensorineural hearing loss. Unfortunately, a hearing aid does not restore hearing to normal. A hearing aid should, however, significantly improve a person's ability to communicate and enjoy sounds.' [9] Hearing Aids: Amplifying the Sound

[Figure 9 Diagram showing the different types of hearing aids]

'Most profoundly deaf people who cannot hear sounds even with a hearing aid benefit from a cochlear implant. Cochlear implants provide electrical signals directly into the auditory nerve by means of multiple electrodes inserted into the cochlea, which is the inner ear structure containing the auditory nerve. An external microphone and processor pick up sound signals and convert them to electrical impulses. The impulses are transmitted electromagnetically by an external coil through the skin to an internal coil, which connects to the electrodes. The electrodes stimulate the auditory nerve.' [10] http://www.thanaamoolla.co.za/images/cochlear%20implant_1.jpg

[Figure 10 diagram showing the full set up of a cochlea implant]

However further tests are first carried out to check that the patient should be considered for an implant as shown in figure 11 below.

http://www.nciua.org.uk/ufiles/image/31(1).jpg

[Figure 11 a graph showing the frequencies and threshold levels considered for a cochlea implant]

Hypothesis:

With increasing age the efficiency in the functioning of the human ear cochlea reduces for both woman and men. It can be predicted that the efficiency reduction is greater for men than for women.

It is observed that with an increase in the loudness of sound, the functioning of the human ear cochlea can be affected causing many temporary and/or permanent hearing problems and thus it can be predicted that along with increasing age, the need for an increase in the loudness of sound to hear efficiently will be required for humans with increasing age and distance. Men will require the loudness of the sound to be greater than woman with increasing distances and age.

All these factors could affect the function with varying importance. However these predictions can face some limitations in the form of every human's job occupation and daily lifestyle, whether they are exposed to high intensity sounds or if they face only sound frequencies found in the tolerable human ear threshold of hearing.

Equipment/Materials/Resources:

Ten subjects from both genders for experimentation between the age groups of 10-19 years old, 20-29 years old, 30-39 years old and 40-49 years. Subjects with known hearing and any other disabilities were not used in this investigation due to the ethical implications behind this. Subjects under the age of 10 cannot be used as there is a high chance of human error when collecting the required readings. Subjects above the age 49 were not used as the observations in a trial showed inconsistency.

Headphones able to play music at varying volumes and thus varying sound frequencies. Headphones will direct the sound waves in a minimal direction whereas speakers will spread the sound waves out, this can cause interference in the music and lead to superposition of the sound waves if more than one speaker is used.

Metre ruler.

A clamp stand and clamp.

A high flat table.

iPod nano 16GB Purple (5th generation) produced by Apple.

Sound level meter model SL-4010.

Procedure:

To analyse in depth and to understand as to how can age, gender and loudness of sound potentially can have an influence on the functioning of the human ear cochlea, a suitable method was developed.

Select one male or female subject from one of the age categories, 10-19 years old, 20-29 years old, 30-39 years old or 40-49 years.

The Subject is seated in a room where there are no sound distractions next to a table with a clamp stand and clamp positioned securely on the table.

The headphone is positioned in line with the Subject's ear firstly at a distance of 15 cm using the metre ruler; it is kept perfectly straight to reduce the chance of any errors in measurement. A headphone connected to the iPod music player is fixed tightly in the clamp, in line with the Subject's ear. The distance is measured from the Subject's ear in the correct line within which the sound waves from the headphone will travel by adjusting the height of the ruler's position.

First a piece of music with a high frequency and thus a high sound intensity is played from first 0-volume and increasing till the Subject can hear the music. The volume level percentage is recorded for the correct distance, along with their age and gender. After which the relative sound intensity for the volume percentage is calculated using a sound level meter. The piece of music chosen is "Here comes the boom" which is a soundtrack song for the movie "The Longest Yard (2005)" by the artist "Nelly" as it has a high loudness level.

Next with the same method (step 4), a piece of music with a low frequency and thus a low sound intensity is played and appropriate results recorded. The piece of music chosen is "If you come back" by the band "Blue," from the album "Best of Blue" produced in 2004 and is copyrighted by "Virgin Records" as it has a low loudness level.

Once both pieces of music have been played at a distance of 15 cm, the distance is increased by a further 15 cm and the above method repeated. The distance is increased up to 60 cm only. (See figure 12 below).

Once one Subject is experimented on, the same method (steps 4, 5 and 6) is repeated on the remaining Subjects using ten male and ten female Subjects from each age group with the correct ages.

For each subject the same type of scatter graph is plotted. Sound intensity level (dB) is plotted on the y axis and distance (cm) on the x axis. On the graph the results for both types of music are plotted and labelled in different colours to allow easy differentiation between the points.

Subject's ear

Ruler

Headphone

I:\DCIM\101MSDCF\DSC03394.JPG

Clamp and clamp stand

iPod volume percentage level

Ruler

Headphone

Sound intensity level meter with reading and microphone[Figure 12 showing the set up used for experimentation using a subject from the selected age group]I:\DCIM\101MSDCF\DSC03396.JPG

[Figure 13 Showing the set up used for measuring the sound intensity level using a sound level meter and the volume level on the iPod music player]

Results:

Tables:

 

 

 

 

 

Loud Music

 

Soft Music

 

Distance (cm) ± 0.05

Subject no.

Age Group (years old)

Age (years old)

Gender

Volume Level (%)

± 5 %

Sound Intensity Level (dB)

Volume Level (%)

± 5 %

Sound Intensity Level (dB)

15

1

10 to 19

10

M

10

41.0

15

41.0

15

1

10 to 19

10

F

15

42.4

20

42.3

15

2

10 to 19

11

M

15

42.4

20

42.3

15

2

10 to 19

11

F

15

42.4

25

43.1

15

3

10 to 19

12

M

15

42.4

25

42.3

15

3

10 to 19

12

F

15

42.4

10

40.9

15

4

10 to 19

13

M

15

42.4

20

42.3

15

4

10 to 19

13

F

20

43.5

20

42.3

15

5

10 to 19

14

M

20

43.5

25

44.0

15

5

10 to 19

14

F

20

43.5

25

43.1

15

6

10 to 19

15

M

25

44.0

35

44.9

15

6

10 to 19

15

F

20

43.5

25

43.1

15

7

10 to 19

16

M

25

44.0

35

44.9

15

7

10 to 19

16

F

20

43.5

25

43.1

15

8

10 to 19

17

M

30

44.2

45

48.2

15

8

10 to 19

17

F

20

43.5

30

44.2

15

9

10 to 19

18

M

35

46.9

50

47.5

15

9

10 to 19

18

F

25

44.0

35

44.9

15

10

10 to 19

19

M

40

47.2

45

48.2

15

10

10 to 19

19

F

20

43.5

30

44.2

15

11

10 to 19

20

M

35

46.9

45

48.2

15

11

10 to 19

20

F

40

47.2

30

44.2

15

12

10 to 19

21

M

30

44.2

40

46.1

15

12

10 to 19

21

F

30

44.2

40

46.1

15

13

10 to 19

22

M

40

47.2

40

46.1

15

13

10 to 19

22

F

25

44.0

35

44.9

15

14

10 to 19

23

M

50

50.2

55

47.9

15

14

10 to 19

23

F

35

46.9

35

44.9

15

15

10 to 19

24

M

30

44.2

35

44.9

15

15

10 to 19

24

F

30

44.2

35

44.9

15

16

10 to 19

25

M

40

47.2

45

48.2

15

16

10 to 19

25

F

40

47.2

50

47.5

15

17

10 to 19

26

M

40

47.2

60

48.2

15

17

10 to 19

26

F

40

47.2

45

48.2

15

18

10 to 19

27

M

25

44.0

40

47.2

15

18

10 to 19

27

F

35

46.9

45

48.2

15

19

10 to 19

28

M

40

47.2

50

47.5

15

19

10 to 19

28

F

40

47.2

45

48.2

15

20

10 to 19

29

M

50

50.2

55

47.9

15

20

10 to 19

29

F

50

50.2

60

48.2

15

21

10 to 19

30

M

45

47.8

45

48.2

15

21

10 to 19

30

F

45

47.8

45

48.2

15

22

10 to 19

31

M

45

47.8

50

47.5

15

22

10 to 19

31

F

55

50.9

45

48.2

15

23

10 to 19

32

M

50

50.2

60

48.2

15

23

10 to 19

32

F

30

44.2

35

44.9

15

24

10 to 19

33

M

45

47.8

50

47.5

15

24

10 to 19

33

F

35

46.9

50

47.5

15

25

10 to 19

34

M

60

51.0

70

50.0

15

25

10 to 19

34

F

40

47.2

50

47.5

15

26

10 to 19

35

M

50

50.2

50

47.5

15

26

10 to 19

35

F

50

50.2

50

47.5

15

27

10 to 19

36

M

55

50.9

60

48.2

15

27

10 to 19

36

F

65

52.5

85

54.2

15

28

10 to 19

37

M

55

50.9

60

48.2

15

28

10 to 19

37

F

50

50.2

70

50.0

15

29

10 to 19

38

M

70

55.2

75

51.2

15

29

10 to 19

38

F

60

51.0

65

49.6

15

30

10 to 19

39

M

70

55.2

80

53.4

15

30

10 to 19

39

F

50

50.2

65

49.6

15

31

10 to 19

40

M

75

58.8

80

53.4

15

31

10 to 19

40

F

40

47.2

60

51.0

15

32

10 to 19

41

M

80

60.2

85

54.2

15

32

10 to 19

41

F

30

44.2

50

50.2

15

33

10 to 19

42

M

55

50.9

80

60.2

15

33

10 to 19

42

F

40

47.2

60

48.2

15

34

10 to 19

43

M

65

52.5

90

55.3

15

34

10 to 19

43

F

60

51.0

70

50.0

15

35

10 to 19

44

M

65

52.5

75

51.2

15

35

10 to 19

44

F

55

50.9

60

48.2

15

36

10 to 19

45

M

70

55.2

80

53.4

15

36

10 to 19

45

F

60

51.0

70

50.0

15

37

10 to 19

46

M

85

61.4

90

55.3

15

37

10 to 19

46

F

80

60.2

90

55.3

15

38

10 to 19

47

M

45

47.8

80

53.4

15

38

10 to 19

47

F

50

50.2

70

50.0

15

39

10 to 19

48

M

70

55.2

80

53.4

15

39

10 to 19

48

F

90

63.1

95

56.1

15

40

10 to 19

49

M

90

63.1

95

56.1

15

40

10 to 19

49

F

75

58.8

85

54.2

[Figure 14 Table of collected data for age group 10-19 at 15 cm distance]

Loud Music

 

Soft Music

 

Distance (cm) ± 0.05

Subject no.

Age Group (years old)

Age (years old)

Gender

Volume Level (%) ± 5 %

Sound Intensity Level (dB)

Volume Level (%) ± 5 %

Sound Intensity Level (dB)

30

1

20 to 29

10

M

10

41.2

20

36.9

30

1

20 to 29

10

F

15

41.9

20

36.9

30

2

20 to 29

11

M

15

42.4

20

42.3

30

2

20 to 29

11

F

20

42.2

30

37.7

30

3

20 to 29

12

M

15

41.9

30

37.7

30

3

20 to 29

12

F

20

42.2

15

36.2

30

4

20 to 29

13

M

20

42.4

25

44.0

30

4

20 to 29

13

F

20

42.2

25

37.5

30

5

20 to 29

14

M

25

43.2

30

37.7

30

5

20 to 29

14

F

25

43.2

30

37.7

30

6

20 to 29

15

M

35

46.1

45

41.2

30

6

20 to 29

15

F

35

46.1

30

37.7

30

7

20 to 29

16

M

30

45.4

45

41.2

30

7

20 to 29

16

F

35

46.1

30

37.7

30

8

20 to 29

17

M

45

49.2

55

43.4

30

8

20 to 29

17

F

25

43.2

30

37.7

30

9

20 to 29

18

M

40

48.7

55

43.4

30

9

20 to 29

18

F

30

45.4

35

39.9

30

10

20 to 29

19

M

45

49.2

50

42.4

30

10

20 to 29

19

F

30

45.4

35

39.9

30

11

20 to 29

20

M

40

48.7

50

42.4

30

11

20 to 29

20

F

45

49.2

35

39.9

30

12

20 to 29

21

M

35

46.1

45

41.2

30

12

20 to 29

21

F

30

45.4

45

41.2

30

13

20 to 29

22

M

40

48.7

45

41.2

30

13

20 to 29

22

F

25

43.2

40

40.0

30

14

20 to 29

23

M

55

51.8

60

44.0

30

14

20 to 29

23

F

35

46.1

40

40.0

30

15

20 to 29

24

M

35

46.1

35

39.9

30

15

20 to 29

24

F

35

46.1

40

40.0

30

16

20 to 29

25

M

40

48.7

50

42.4

30

16

20 to 29

25

F

45

49.2

55

43.4

30

17

20 to 29

26

M

45

49.2

65

44.7

30

17

20 to 29

26

F

45

49.2

45

41.2

30

18

20 to 29

27

M

35

46.1

45

41.2

30

18

20 to 29

27

F

40

48.7

50

42.4

30

19

20 to 29

28

M

50

51.3

55

43.4

30

19

20 to 29

28

F

45

49.2

45

41.2

30

20

20 to 29

29

M

50

45.4

60

44.0

30

20

20 to 29

29

F

55

51.8

65

44.7

30

21

20 to 29

30

M

45

49.2

50

42.4

30

21

20 to 29

30

F

55

51.8

50

42.4

30

22

20 to 29

31

M

50

51.3

55

43.4

30

22

20 to 29

31

F

55

51.8

50

42.4

30

23

20 to 29

32

M

55

51.8

65

44.7

30

23

20 to 29

32

F

35

46.1

40

40.0

30

24

20 to 29

33

M

50

51.3

55

43.4

30

24

20 to 29

33

F

35

46.1

55

43.4

30

25

20 to 29

34

M

60

52.8

75

47.7

30

25

20 to 29

34

F

40

48.7

55

43.4

30

26

20 to 29

35

M

50

51.3

55

43.4

30

26

20 to 29

35

F

50

51.3

55

43.4

30

27

20 to 29

36

M

60

52.8

65

44.7

30

27

20 to 29

36

F

70

54.6

90

51.5

30

28

20 to 29

37

M

55

51.8

65

44.7

30

28

20 to 29

37

F

55

51.8

75

47.7

30

29

20 to 29

38

M

75

55.8

80

48.0

30

29

20 to 29

38

F

65

53.1

70

46.5

30

30

20 to 29

39

M

75

55.8

80

48.0

30

30

20 to 29

39

F

55

51.8

70

46.5

30

31

20 to 29

40

M

80

56.0

85

49.2

30

31

20 to 29

40

F

50

42.4

65

42.4

30

32

20 to 29

41

M

80

56.0

90

51.5

30

32

20 to 29

41

F

40

48.7

60

44.0

30

33

20 to 29

42

M

70

54.6

90

51.5

30

33

20 to 29

42

F

55

51.8

60

44.0

30

34

20 to 29

43

M

70

54.6

95

52.1

30

34

20 to 29

43

F

65

53.1

75

47.7

30

35

20 to 29

44

M

70

54.6

80

48.0

30

35

20 to 29

44

F

65

53.1

70

46.5

30

36

20 to 29

45

M

65

53.1

80

48.0

30

36

20 to 29

45

F

75

55.8

75

47.7

30

37

20 to 29

46

M

90

59.9

95

52.9

30

37

20 to 29

46

F

85

58.8

90

51.5

30

38

20 to 29

47

M

55

51.8

95

52.9

30

38

20 to 29

47

F

55

51.8

80

48.0

30

39

20 to 29

48

M

80

56.0

85

49.2

30

39

20 to 29

48

F

95

61.0

95

52.9

30

40

20 to 29

49

M

95

61.0

100

53.1

30

40

20 to 29

49

F

85

58.5

90

51.5

[Figure 15 Table of collected data for age group 20-29 at 30 cm distance]

 

 

 

 

 

Loud Music

 

Soft Music

 

Distance (cm) ± 0.05

Subject no.

Age Group (years old)

Age (years old)

Gender

Volume Level (%) ± 5 %

Sound Intensity Level (dB)

Volume Level (%) ± 5 %

Sound Intensity Level (dB)

45

1

30 to 39

10

M

15

43.1

20

36.7

45

1

30 to 39

10

F

20

44.5

25

38.0

45

2

30 to 39

11

M

20

44.5

25

36.7

45

2

30 to 39

11

F

20

44.5

35

39.8

45

3

30 to 39

12

M

25

46.0

35

38.7

45

3

30 to 39

12

F

25

46.0

25

38.0

45

4

30 to 39

13

M

25

46.0

30

44.2

45

4

30 to 39

13

F

25

46.0

30

38.8

45

5

30 to 39

14

M

35

49.2

35

39.8

45

5

30 to 39

14

F

30

47.8

30

38.8

45

6

30 to 39

15

M

45

51.2

50

41.2

45

6

30 to 39

15

F

30

47.8

35

39.8

45

7

30 to 39

16

M

45

51.2

50

41.0

45

7

30 to 39

16

F

30

47.8

35

39.8

45

8

30 to 39

17

M

55

53.9

60

43.1

45

8

30 to 39

17

F

30

47.8

35

39.8

45

9

30 to 39

18

M

45

51.2

60

43.1

45

9

30 to 39

18

F

35

49.2

40

40.5

45

10

30 to 39

19

M

50

53.1

55

42.9

45

10

30 to 39

19

F

35

49.2

40

40.5

45

11

30 to 39

20

M

45

51.2

55

42.9

45

11

30 to 39

20

F

50

53.9

40

40.5

45

12

30 to 39

21

M

40

50.6

50

41.2

45

12

30 to 39

21

F

35

49.2

45

41.0

45

13

30 to 39

22

M

45

51.2

50

41.2

45

13

30 to 39

22

F

30

47.8

45

41.0

45

14

30 to 39

23

M

60

54.7

65

44.0

45

14

30 to 39

23

F

40

50.6

45

41.0

45

15

30 to 39

24

M

40

50.6

40

40.5

45

15

30 to 39

24

F

40

50.6

45

41.0

45

16

30 to 39

25

M

40

50.6

50

41.2

45

16

30 to 39

25

F

50

53.9

60

43.1

45

17

30 to 39

26

M

50

53.1

65

44.0

45

17

30 to 39

26

F

50

53.9

50

41.2

45

18

30 to 39

27

M

40

50.6

50

41.2

45

18

30 to 39

27

F

45

51.2

55

42.9

45

19

30 to 39

28

M

55

53.9

60

43.1

45

19

30 to 39

28

F

50

53.9

50

41.2

45

20

30 to 39

29

M

55

53.9

65

44.0

45

20

30 to 39

29

F

60

54.7

70

45.7

45

21

30 to 39

30

M

50

53.9

55

42.9

45

21

30 to 39

30

F

60

54.7

55

42.9

45

22

30 to 39

31

M

55

53.9

65

44.0

45

22

30 to 39

31

F

60

54.7

55

42.9

45

23

30 to 39

32

M

55

53.9

70

45.7

45

23

30 to 39

32

F

40

50.6

45

41.0

45

24

30 to 39

33

M

55

53.9

60

43.1

45

24

30 to 39

33

F

40

50.6

55

42.9

45

25

30 to 39

34

M

65

55.1

80

47.6

45

25

30 to 39

34

F

45

51.2

65

44.0

45

26

30 to 39

35

M

55

53.9

60

43.1

45

26

30 to 39

35

F

55

53.9

65

44.0

45

27

30 to 39

36

M

65

55.1

75

46.5

45

27

30 to 39

36

F

75

57.2

95

50.2

45

28

30 to 39

37

M

65

55.1

65

44.0

45

28

30 to 39

37

F

55

51.2

80

47.6

45

29

30 to 39

38

M

80

58.0

85

48.2

45

29

30 to 39

38

F

70

56.5

75

46.5

45

30

30 to 39

39

M

80

58.0

85

48.2

45

30

30 to 39

39

F

55

53.9

75

46.5

45

31

30 to 39

40

M

85

59.1

90

49.7

45

31

30 to 39

40

F

55

53.9

70

45.7

45

32

30 to 39

41

M

85

59.1

95

50.2

45

32

30 to 39

41

F

50

51.2

65

44.0

45

33

30 to 39

42

M

85

59.1

95

50.2

45

33

30 to 39

42

F

55

53.9

65

44.0

45

34

30 to 39

43

M

75

57.2

95

50.2

45

34

30 to 39

43

F

55

53.9

85

48.2

45

35

30 to 39

44

M

70

56.5

85

48.2

45

35

30 to 39

44

F

70

56.5

75

46.5

45

36

30 to 39

45

M

70

56.5

85

48.2

45

36

30 to 39

45

F

80

58.0

80

47.6

45

37

30 to 39

46

M

95

60.0

100

52.1

45

37

30 to 39

46

F

90

59.8

95

50.2

45

38

30 to 39

47

M

65

55.1

95

50.2

45

38

30 to 39

47

F

70

56.5

85

48.2

45

39

30 to 39

48

M

85

59.1

90

49.7

45

39

30 to 39

48

F

100

61.8

100

52.1

45

40

30 to 39

49

M

100

61.8

95

50.2

45

40

30 to 39

49

F

90

59.8

100

52.1

[Figure 15 Table of collected data for age group 30-39 at 45 cm distance]

 

 

 

 

 

Loud Music

 

Soft Music

 

Distance (cm) ± 0.05

Subject no.

Age Group (years old)

Age (years old)

Gender

Volume Level (%) ± 5 %

Sound Intensity Level (dB)

Volume Level (%) ± 5 %

Sound Intensity Level (dB)

60

1

40 to 49

10

M

25

46.9

25

33.2

60

1

40 to 49

10

F

20

35.9

25

33.2

60

2

40 to 49

11

M

25

36.7

30

33.0

60

2

40 to 49

11

F

35

39.1

35

37.5

60

3

40 to 49

12

M

30

38.8

40

47.2

60

3

40 to 49

12

F

30

38.8

35

37.5

60

4

40 to 49

13

M

30

38.8

35

46.9

60

4

40 to 49

13

F

25

36.7

30

35.0

60

5

40 to 49

14

M

40

41.2

45

39.2

60

5

40 to 49

14

F

35

39.1

35

37.5

60

6

40 to 49

15

M

50

44.0

55

41.3

60

6

40 to 49

15

F

40

41.2

40

38.7

60

7

40 to 49

16

M

55

45.1

60

42.9

60

7

40 to 49

16

F

40

41.2

40

38.7

60

8

40 to 49

17

M

65

47.4

65

43.5

60

8

40 to 49

17

F

35

39.1

40

38.7

60

9

40 to 49

18

M

55

45.1

65

43.5

60

9

40 to 49

18

F

45

42.8

45

39.2

60

10

40 to 49

19

M

50

44.0

60

42.9

60

10

40 to 49

19

F

40

41.2

45

39.2

60

11

40 to 49

20

M

50

44.0

65

43.5

60

11

40 to 49

20

F

55

45.1

50

41.0

60

12

40 to 49

21

M

45

42.8

55

41.3

60

12

40 to 49

21

F

40

41.2

50

41.0

60

13

40 to 49

22

M

50

44.0

60

42.9

60

13

40 to 49

22

F

35

39.1

45

39.2

60

14

40 to 49

23

M

65

47.4

65

43.5

60

14

40 to 49

23

F

45

42.8

50

41.0

60

15

40 to 49

24

M

45

42.8

45

39.2

60

15

40 to 49

24

F

45

42.8

50

41.0

60

16

40 to 49

25

M

45

42.8

55

41.3

60

16

40 to 49

25

F

55

45.1

65

43.5

60

17

40 to 49

26

M

55

45.1

70

44.8

60

17

40 to 49

26

F

55

45.1

55

41.3

60

18

40 to 49

27

M

45

42.8

60

42.9

60

18

40 to 49

27

F

50

44.0

55

41.3

60

19

40 to 49

28

M

60

46.9

60

42.9

60

19

40 to 49

28

F

55

45.1

55

41.3

60

20

40 to 49

29

M

55

45.1

65

43.5

60

20

40 to 49

29

F

65

47.4

70

44.8

60

21

40 to 49

30

M

50

44.0

65

43.5

60

21

40 to 49

30

F

65

47.4

60

42.9

60

22

40 to 49

31

M

60

46.9

65

43.5

60

22

40 to 49

31

F

65

47.4

60

42.9

60

23

40 to 49

32

M

60

46.9

70

44.8

60

23

40 to 49

32

F

45

46.9

50

41.0

60

24

40 to 49

33

M

55

45.1

70

44.8

60

24

40 to 49

33

F

50

44.0

60

42.9

60

25

40 to 49

34

M

70

49.3

85

47.7

60

25

40 to 49

34

F

45

42.8

65

43.5

60

26

40 to 49

35

M

55

45.1

65

43.5

60

26

40 to 49

35

F

60

46.9

70

44.8

60

27

40 to 49

36

M

70

49.3

75

45.0

60

27

40 to 49

36

F

80

51.9

100

49.5

60

28

40 to 49

37

M

65

47.4

70

44.8

60

28

40 to 49

37

F

60

46.9

85

47.7

60

29

40 to 49

38

M

85

52.8

90

48.3

60

29

40 to 49

38

F

70

49.3

80

46.1

60

30

40 to 49

39

M

80

51.9

95

49.0

60

30

40 to 49

39

F

65

47.4

75

45.0

60

31

40 to 49

40

M

85

52.8

90

48.3

60

31

40 to 49

40

F

65

47.4

70

44.8

60

32

40 to 49

41

M

90

53.1

95

49.0

60

32

40 to 49

41

F

55

45.1

70

44.8

60

33

40 to 49

42

M

90

53.1

100

49.5

60

33

40 to 49

42

F

70

49.3

70

44.8

60

34

40 to 49

43

M

80

51.9

100

49.5

60

34

40 to 49

43

F

70

49.3

90

48.3

60

35

40 to 49

44

M

80

51.9

90

48.3

60

35

40 to 49

44

F

80

51.9

85

47.7

60

36

40 to 49

45

M

85

52.8

100

49.5

60

36

40 to 49

45

F

90

53.1

85

47.7

60

37

40 to 49

46

M

100

55.9

100

49.5

60

37

40 to 49

46

F

95

54.0

100

49.5

60

38

40 to 49

47

M

75

50.1

100

49.5

60

38

40 to 49

47

F

80

51.9

95

49.0

60

39

40 to 49

48

M

90

53.1

95

49.0

60

39

40 to 49

48

F

100

55.9

100

49.5

60

40

40 to 49

49

M

100

55.9

100

49.5

60

40

40 to 49

49

F

100

55.9

100

49.5

[Figure 16 Table of collected data for age group 40-49 at 60 cm distance]

Graphs:

For the graphs below, the points fixed for series 1 show the sound intensity level for loud music and series 2 show the sound intensity level for soft music.

Analysis and Evaluation:

The experiments carried out only investigated the affect of loud and soft music and their intensity levels on the functioning of the ear. As seen in figure 8, all vowels and consonants in the alphabet have different frequencies which the ear can distinguish between unless they suffer from any hearing loss. Music and speech have differing qualities as their wave form differ in size according to the loudness, pitch, bass, treble and type of music, see figure 2. If the experiment also included the usage of recorded speech at varying volumes, this discrimination could also have been observed and lead to further inquiry into new hearing aid designs.

The observation of the how the variables may influence the functioning of the ear was completed in a closed room with external sound kept to a minimum to allow the recording of accurate data. Natural and man-made background noise is hard to limit, a reading of 0 sound intensity level cannot be achieved on a decibel meter, some sounds could have easily distracted the Subject being tested and affected the readings recorded. The humming sound released from the light source in the room could not be controlled. If the Subjects had been tested in a sound proof room such as a recording studio this error could have been limited.

The instruments used also had their limitations and uncertainties which may have affected the data collected and lead to minimum systematic errors. Temperature of the room could have affected the concentration of the Subject being tested along with the calibration and accuracy of the decibel meter. The quality of the headphones used could have been a factor while measuring the relative volume percentage level as the headphones efficiency may have been low. Measuring the volume from the sound source was an approximate value was taken according to what was displayed on the screen. If the music was played through a scientific software, an increase in the accuracy and precision of the data o

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