Short Answer

The audible range for humans is the range of sound frequencies that a normal human ear can hear. This range lies between 20 Hz and 20,000 Hz (20 kHz). Sounds below 20 Hz are called infrasonic, and sounds above 20,000 Hz are called ultrasonic, both of which humans cannot hear.

Children and young people usually hear higher frequencies better than older people. As age increases, the upper limit of hearing decreases. Most everyday sounds, such as speech and music, fall within the human audible range.

Detailed Explanation :

Audible range for humans

The audible range for humans refers to the specific band of sound frequencies that the human ear is capable of detecting. Sound travels in the form of waves, and each wave has a frequency, which is the number of vibrations occurring in one second. The human ear is designed in such a way that it can sense only those vibrations that lie between certain limits. These limits are known as the lower limit and upper limit of hearing.

For most people with normal hearing, the audible range extends from 20 Hz to 20,000 Hz. This means humans can hear sounds whose frequency is at least 20 vibrations per second and at most 20,000 vibrations per second. Anything below 20 Hz is infrasonic, and anything above 20,000 Hz is ultrasonic. These types of sounds may exist in nature, but human ears cannot detect them.

This hearing range is not fixed for every person. Age, health, and exposure to loud noise can affect hearing ability. Young children often have a better upper limit and may hear frequencies slightly above 20 kHz. With age, the upper limit slowly decreases. This is why elderly people may not hear high-pitched sounds like a mosquito buzzing or very sharp electronic beeps.

Lower limit and upper limit of hearing

Lower limit – 20 Hz
The sounds below 20 Hz have very slow vibrations. Humans cannot hear them, but they may feel them as vibrations. Earthquakes, rumbling machines, and ocean waves sometimes create infrasonic sounds.
Upper limit – 20,000 Hz
Sounds above 20 kHz vibrate very rapidly. Humans cannot hear these sounds, but many animals can. Bats use ultrasonic frequencies for navigation. Dolphins and dogs can hear higher frequencies than humans.

The ability of the ear to detect frequencies depends on the sensitivity of the eardrum and the inner ear structures. If vibrations are too slow or too fast, the ear cannot convert them into signals for the brain.

Importance of the audible range

Understanding the audible range helps in many areas of science and daily life:

Speech and communication: Human speech generally lies between 250 Hz and 3000 Hz, well within the audible range.
Music: Musical instruments produce frequencies that can be comfortably heard by humans.
Technology: Devices like telephones, microphones, and speakers are designed to work within the human hearing range.
Health: Hearing tests check how well a person can hear different frequencies within the audible range.
Safety: Alarm sounds are created within the audible range so humans can detect them quickly during emergencies.

Examples of sounds within the audible range

Human voice: 80–3000 Hz
Guitar notes: around 80–1200 Hz
Dog barking: 500–2000 Hz
School bell: around 1000 Hz
Traffic noise: 100–500 Hz

These sounds fall comfortably within the frequency limits that humans can hear.

Why some sounds fall outside the audible range

Nature produces many sounds that humans cannot hear:

Infrasonic sounds: Produced by earthquakes, storms, volcanoes, and some large animals.
Ultrasonic sounds: Used by bats for echolocation, by dolphins underwater, and by some machines.

Even though humans cannot hear these sounds, they play an important role in the environment and in technology. For example, ultrasound is used in medical imaging. Sonar uses ultrasonic waves to detect objects underwater.

Variation with age and conditions

The audible range is highest at birth. As a person grows older, especially after the age of 40 or 50, the upper limit gradually decreases. Exposure to loud music or machines can also reduce hearing ability. This loss is usually more noticeable at higher frequencies.

People with hearing difficulties may have a smaller audible range. Hearing aids help them by amplifying frequencies they cannot detect well.

Conclusion

The audible range for humans is 20 Hz to 20,000 Hz, which represents the limits of sound frequencies the human ear can hear. Sounds below this range are infrasonic, and sounds above it are ultrasonic. This range allows us to enjoy speech, music, and everyday sounds. Although hearing ability changes with age and health, the audible range remains an essential concept in physics and daily life.