Hearing is one of the five senses of the human body, enabled by the ear. Ears pick up sounds as vibrations and then translate this information into a form for the brain to understand. Unlike other senses, this is a completely mechanical process.

Hearing loss is often associated with age. Many elderly people wear hearing aids, which leads to the suggestion that hearing deteriorates with age. Research shows that the main aspect of hearing loss that occurs is high frequencies. There have been many tests on what causes hearing loss; however, no test has confirmed that hearing may also be different between males and females.

The aim of this experiment is to find out whether there is a difference in hearing threshold between genders and if so, find out which gender has the better hearing. This experiment tests people from a range of ages and both genders. The experiment involves finding the highest sound each person can hear, and therefore finding the upper threshold of each individual’s hearing.

Background Research:

Sound waves

Sound and music are parts of our everyday sensory experience. Just as we have eyes for the detection of light and color, so we are equipped with ears for the detection of sound. The basis for an understanding of sound, music and hearing is the physics of waves. Sound is a wave which is created by vibrating objects and goes through a medium from one location to another.

Sound waves are longitudinal waves. Longitudinal waves are when the particles of the medium move in a direction parallel to the direction of energy. Since air molecules (the particles of the medium) are moving in a direction which is parallel to the direction which the wave moves, the sound wave is referred to as a longitudinal wave.

A sound wave, like any other wave, is introduced into a medium by a vibrating object. The particles of the medium through which the sound moves is vibrating in a back and forth motion at a given frequency. The frequency of a wave refers to how often the particles of the medium vibrate when a wave passes through the medium.

The frequency of a wave is measured as the number of complete back-and-forth vibrations of a particle of the medium per unit of time. A commonly used unit for frequency is the Hertz (abbreviated Hz), where 1 Hertz = 1 vibration/second. The frequency of a sound wave not only refers to the number of back-and-forth vibrations of the particles per unit of time, but also refers to the number of waves which pass a given point per unit of time.

The Human Ear

The ears of humans (and other animals) are sensitive detectors capable of detecting the fluctuations in air pressure. The human ear is capable of detecting sound waves with a wide range of frequencies, ranging between approximately 20 Hz to 20 000 Hz.

These frequencies are commonly referred to as the pitch of a sound. A high pitch sound corresponds to a high frequency and a low pitch sound corresponds to a low frequency.

The ear consists of three main parts – the outer ear, the middle ear, and the inner ear. Each part of the ear serves a specific purpose in the task of detecting and interpreting sound. The middle ear serves to transform the energy of a sound wave into the internal vibrations of the bone structure of the middle ear and ultimately transform these vibrations into a compression wave in the inner ear. The inner ear serves to transform the energy of a compression wave within the inner ear fluid into nerve impulses which can be transmitted to the brain.

Outer Ear

The outer ear serves to collect and channel sound to the middle ear. The outer ear consists of an ear flap (pinna) and an approximately 2-cm long ear canal. The pinna provides protection for the middle ear in order to prevent damage to the eardrum. The outer ear also channels sound waves which reach the ear through the ear canal to the eardrum of the middle ear.

Middle Ear

The middle ear is an air-filled cavity which consists of an eardrum and three tiny, interconnected bones – the hammer, anvil, and stirrup. The eardrum is a very durable and tightly stretched membrane which vibrates as the incoming pressure waves reach it, vibrating the eardrum at the same frequency of the sound wave. Being connected to the hammer, the movements of the eardrum will set the hammer, anvil, and stirrup into motion at the same frequency of the sound wave. The stirrup is connected to the inner ear. The three tiny bones of the middle ear act as levers to amplify the vibrations of the sound wave.

Inner Ear

The inner ear consists of a cochlea, the semicircular canals, and the auditory nerve. The cochlea and the semicircular canals are filled with a water-like fluid. The cochlea is a snail-shaped organ which would stretch to approximately 3 cm. In addition to being filled with fluid, the inner surface of the cochlea is lined with over 20 000 hair-like nerve cells which perform one of the most critical roles in our ability to hear. As a sound wave moves from the interface between the hammer of the middle ear and the oval window of the inner ear through the cochlea, the small hair-like nerve cells will be set in motion.

When the frequency of the sound wave matches the natural frequency of a nerve cell (each nerve cell has a slightly different length), that nerve cell will resonate with larger amplitude of vibration. This induces the cell to release an electrical impulse which passes along the auditory nerve towards the brain. In a process which is not clearly understood, the brain is capable of interpreting the qualities of the sound upon reception of these electric nerve impulses.

Hearing Loss

Hearing loss can vary. It may only affect a person’s ability to hear only loud sound or particularly high or low frequencies. It may vary between ears and could happen suddenly or slowly.

Hearing loss can be categorized by what part of the auditory system is damaged. There are three basic types of hearing loss: conductive hearing loss, sensorineural hearing loss and mixed hearing loss.

Conductive Hearing Loss

Conductive hearing loss occurs when sound is not conducted efficiently through the outer ear canal to the eardrum. 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 medically or surgically corrected.

Sensorineural Hearing Loss

Sensorineural hearing loss occurs when there is damage to the inner ear or to the nerve pathways from the inner ear to the brain. Sensorineural hearing loss cannot be medically or surgically corrected. It is a permanent loss. Because the process of hearing loss is gradual, people who have it may not realize that their hearing is diminishing. It can be caused by the cumulative effects of repeated exposure to daily traffic sounds or construction work, noisy offices, equipment that produces noise, and loud music can. Sensorineural hearing loss is most often due to a loss of hair cells in the inner ear. This can occur as a result of hereditary factors as well as aging, various health conditions, and side effects of some medicines.

Hearing loss is most commonly associated with aging. Presbycusis is a type of sensorineural loss of hearing that gradually occurs in most people as they grow older. Presbycusis may be caused by changes in the blood supply to the ear because of heart disease, high blood pressure, vascular conditions caused by diabetes, or other circulatory problems. The main loss of hearing occurs in high pitched frequencies. According to statistics, about 30-35 percent of adults between the ages of 65 and 75 years have a hearing loss. It is estimated that 40-50 percent of people 75 and older have a hearing loss. There have been no definite reports that hearing loss is also gender related.

Future Directions

Hearing aids have helped people with hearing loss to have improved hearing. Hearing aids can help with some forms of hearing loss, but not all. Future directions of this topic is finding ways of fixing hearing loss, or preventing it altogether.

Hypothesis and Aim

The aim of this experiment is to see whether females have a higher hearing threshold than males. There is no scientific evidence to prove this; however, the hypothesis (based on a bias opinion) is that females are able to hear higher frequencies than males of the same age.

Method

Used the program “Hearing Test” (made specifically for this experiment) to test the hearing of an individual, facing the computer at a distance of half a meter.

• Played a mid-range frequency of 500 Hz to show the individual what to listen for.
• Jumped to a frequency of 5000 Hz.
• If individual could hear the tone, increased frequency by 1000 Hz until the individual could no longer hear the tone.
• When individual could no longer hear tone, went back to previous frequency.
• Increased frequency by smaller increments such as 100 Hz until the individual could no longer hear the tone.
• Went individual could no loner hear the tone, went back to previous frequency.
• Increased frequency by 10 Hz until the approximate highest frequency that the individual was able to hear was found.
• Repeated twice to confirm the results but with left ear facing the computer then right ear facing the computer.

This experiment tested people from a range of ages and from both genders. The independent variable was the gender. The dependant variable was the hearing thresholds of the people. One control was the location: all people were tested in a quiet room. The distance of the individual from the computer stayed constant. Another controlled variable was the volume of the sound: the program played all tones at the same volume, no matter what the volume of the computer was. To avoid any damage to the ear, the tones were played at a reasonable volume.

Results

A group of individuals were tested and the results for each individual were entered into a spreadsheet as shown below. This enabled the results to be sorted in a variety of ways. The data ranged from as low as 5760 Hz to as high as 24900 Hz.

Name	Age	Gender	High1 (both ears) Hz	High2 (Left ear) Hz	High3 (Right ear) Hz	High Average Hz
Steven	14	Male	24900	24900	24900	24900
Chelsea	6	Female	21900	21900	21900	21900
Paris	9	Female	19660	19660	19660	19660
Jake	12	Male	19530	19530	19530	19530
Alana	13	Male	18990	18990	18990	18990
David	15	Male	18300	18300	18300	18300
Doreen	72	Female	17630	17630	17630	17630
Michael	11	male	17535	17535	17535	17535
Anthony	10	Male	17420	17420	17420	17420
Sammy	5	Male	17400	17400	17400	17400
Fiona	36	Female	17290	17290	17290	17290
Brad	35	Male	17013	17010	17010	17011
Mia	15	Female	16850	16850	16850	16850
Amy	15	Female	16500	16500	16500	16500
Chris	9	Male	16370	16370	16370	16370
Jack	9	Male	16245	16245	16245	16245
Peter	13	Male	16130	16130	16130	16130
Miriam	9	Female	15980	15980	15980	15980
Tim	9	Male	15980	15980	15980	15980
Dylan	15	Male	15800	15800	15800	15800
Despina	15	Female	15780	15780	15780	15780
Byron	14	Male	15600	15600	15600	15600
Carlie	5	Female	15587	15587	15587	15587
Steph	15	Female	15550	15540	15540	15543
Kristy	16	Female	15500	15500	15500	15500
Peta	15	Female	15310	15310	15310	15310
Bridie	6	Female	15100	15100	15100	15100
Andrew	15	Male	14600	14600	14600	14600
Katia	33	Female	14544	14544	14544	14544
Dimitra	44	Female	13990	13990	13990	13990
Tristan	16	Male	13500	13500	13500	13500
Heather	46	Female	13540	12700	12690	12976
John	47	Male	12690	12550	11698	12312
Lynda	42	Female	11940	11940	11940	11940
Ken	41	Male	10100	10100	10100	10100
Paul	50	Male	9160	9100	9150	9136
Joan	73	Female	8030	8980	8750	8586
Fred	74	Male	8140	8600	8130	8290
Wally	76	Male	5770	5740	5790	5766

Observations

During the hearing test, people had tendencies to move their head closer to the computer. This is because as the sound gets higher people reported that the sound got softer. People also described a sensation that they could “feel” the sound in their ears, but not actually hear it. This may be psychological, as they knew a sound was being played, but couldn’t hear it. It may also be because the nerve cells in the inner ear were damaged and did a poor job at sending the signal to the brain.

Gender Differences

This graph shows the hearing test results with gender marked out. The pink dots are females, while the blue dots are males. The females seemed to be at the top of the data, while the males seemed to be lower. This seemed more noticeable for people above the age of 30. The data suggests that females have a slightly higher frequency threshold than males; however there is not enough data to be conclusive.

Age Related Hearing Loss

This XY Scatter graph shows how hearing declines with age. The data formed a linear (straight line) graph and highest frequency had an inverse relationship with age (age increased, highest frequency decreased). There are some outliers, such as 72 year old Doreen, who has a high hearing threshold of 17630 Hz, and Steven Hughes, 14, who has a high hearing threshold of 24900 Hz.

Differences between ears

At about the age of 50, the results showed that hearing declined differently between ears (with the exception of Doreen), as shown below.

Name	Age	Gender	High (both ears)	High (left ear)	High (right ear)	High Average
Paul	50	Male	9160	9100	9150	9136
Doreen	72	Female	17630	17630	17630	17630
Joan	73	Female	8030	8980	8750	8586
Fred	74	Male	8140	8600	8130	8290
Wally	76	Male	5770	5740	5790	5766

This suggested that age related hearing loss affected each ear differently, causing one ear to be able to hear better than the other. This may be the reason why many people turn their head sideways when straining to hear soft or high sounds.

Conclusion

The conclusion to this experiment is inconclusive. It suggests that females may have better hearing than males; however there is not enough data to prove this. This experiment shows a definite relationship between hearing loss and age. Older people could not hear sounds as high as younger people and the data appeared to decrease at a constant rate. Hearing loss affects each ear differently, but it is only evident in older people.

Discussion

There were no difficulties in conduction the experiment. It ran smoothly, however it was surprising how steep that hearing declines with age. It was unexpected to have such a large difference in hearing threshold between ears of older people. If this experiment was to be done again, there would need to be more people tested, even double the amount of people that was tested in this experiment. The people that were tested gave feedback, saying that the tone that was meant to be heard was not long enough. This could be changed to a longer tone or even to a continuous tone until stopped.

Hearing decreased with age because of presbycusis, the hearing disorder associated with age. It appeared to affect most of the individuals tested, rather than the 35% like statistics say. The inability to be able to hear high pitched sounds is a sign of hearing loss and in most cases and its not just high pitched sounds that are affected.

Research on this topic may lead to better production of hearing aids, bionic ears or may even become surgically possible to prevent hearing loss. It may also help with the production of “Under 21” Ring tones, where phone tones are made so that only young people are able to hear them. Mp3 files eliminate any unnecessary sound to try to make the file smaller. The sound mp3s eliminate is generally sound that is outside human hearing thresholds, so the hearing thresholds must be known.

Please note that this data was collected by a test carried out and made by me for a school science project. Due to variables and my inexperience, it may not be completely accurate. There is no guarantee on the reliability of the data. The tests are not conclusive and may be incorrect.