Humans are indeed the most intelligent animals that inhabit this planet. However, our intelligence often deprives us of excelling at other sensory, olfactory and auditory senses. Most animals are way too far ahead of us, when it comes to hearing range. Human hearing range is a set of frequencies that are audible to human ear. Let us understand the working of human ear with respect to the perception of sound.
Perception and Measurement of Sound in Human Ear
Human ear is a complex organ with many small bones and cartilages comprising it. The sound waves enter through the external ear and pass through the tunnel of the ear to hit the eardrum (tympanic membrane). The impact sets this thin membrane in oscillation, causing alternate compressions and rarefaction. This motion also moves other ear bones such as the ossicles, malleus, incus and stapes. Frequency is measured in terms of oscillations of these bones, per second. The unit of frequency is hertz. Typically, 1 Hz = 1 cycle/second.
Human Hearing Range in Normal Conditions
On an average, a human ear can identify and distinguish the sound waves in the range of 20 Hz to 20 kHz (20,000 Hz). However, as you age, the auditory sense on the higher end of the frequency range begins to diminish. It is much lower in older people, while infants and babies are the ones with maximum hearing capacity. The auditory sense for higher frequencies begins to diminish by the age of 8 itself.
Human Hearing in Ideal Conditions
In laboratory, the human hearing range is identified using an audiometer which emits sound waves of various frequencies and a calibrated headphone. Under such ideal conditions, the human ear can pick up the frequencies between 12 Hz to 20 kHz.
Hearing Range in Men and Women
There is a significant difference in the hearing ranges of men and women. It has been found that women are more sensitive towards higher range frequencies than their male counterparts. The perception of lower range frequencies is more or less the same in men and women.
Expressing Hearing Range in Different Scales
Although, frequency scale is the most commonly used scale for expressing human hearing range, it is not uncommon to use pascal (Pa) or decibel (dB) scale. However, pascal scale is unmanageable as it deals with numbers of very large magnitude. It is expressed as uPa, where 1 uPa denotes the distance traveled by sound wave during an oscillation, which is equivalent to one tenth of the diameter of a hydrogen atom. Sound waves in human ear travel a lot more distance than that, thereby making it difficult to express in uPa scale. The softest sound that can be heard by human ear is about 20 uPa. The decibel scale is simpler to express as it is a logarithmic scale, that directly translates the uPa scale. It uses 0 db (20 uPa) as reference scale and goes on compressing the pressure scale. Thus, 20 million uPa translates to only 120 dB. Thus, the human hearing range in dB is 0 dB to 120 dB.
Human hearing range varies extensively from person to person. Thus, to detect hearing loss, it is better to measure the aural range of the person with respect to the referenced scale than with the normal standardized scale. The tests can be performed using advanced auditory diagnostic tools, which can accurately detect and diagnose the causes of hearing loss.