You are sitting in your class, and your teacher is writing on the board using chalk. Sqqqqquuuueeeaaakkkkk — there’s a sudden disturbance as the chalk scratches the board loudly. You automatically put your hands over your ears to escape the loud screeching noise. This is a common scenario you would have faced in your school. Ever wondered why some sounds annoy us or even hurt our ears?
The answer is quite simple, sounds that have a higher frequency are not suitable for human hearing. The typical human hearing frequency range is from approximately 20 Hertz (Hz) to 20,000 Hertz (20 kHz), which represents the span of sound vibrations per second that most people can detect. Sounds with frequencies below 20 Hz are considered infrasonic, while those above 20 kHz are known as ultrasonic. These ultrasonic sounds are extremely sensitive to our ears and can even be painful if heard for a prolonged period.
Did you know?
20 Hz is a very low-frequency sound, like a deep rumble, which we may feel as a vibration more than hear, while 20,000 Hz (20 kHz) is a very high-frequency sound. Young children and infants can sometimes perceive sounds slightly higher than this, but the ability to hear these frequencies generally decreases with age.
How does your ear work?
Sound is a form of energy produced by vibrations, and they are always in wave form. These waves enter the outer ear, and the pinna (the visible part of the ear) helps collect sound waves. The sound waves travel through the ear canal and hit the eardrum (tympanic membrane).
The sound waves make the eardrum vibrate, and the eardrum converts sound waves (air vibrations) into mechanical vibrations. The vibrations then pass from the eardrum to three tiny bones in the middle ear called the ossicles (Malleus (Hammer), Incus (Anvil), Stapes (Stirrup)). These bones amplify the vibrations and pass them to the oval window of the inner ear. Here, if the vibrations are already loud, when amplified, they become too much for the ear to handle, creating damage.
The vibrations from the ossicles cause the fluid inside the cochlea to move. Inside the cochlea, there are tiny hair cells (sensory cells) that convert these fluid movements into electrical signals that are then sent to the brain through auditory nerves.
Did you know?
Ear infections, ear barotrauma caused by sudden changes in pressure, acoustic trauma due to sudden exposure to loud noise or even hyperacusis (heightened sensitivity to everyday sounds, where even normal sound levels cause discomfort or pain) are all medical conditions which can cause pain or irritation in your ear.
Sounds like a chalk scratching over the board, steel utensils falling down, sirens or even door squeaks can feel irritating due to the same reason. Devices like LRAD (Long Range Acoustic Device) often use this concept to disperse protesters, as a protection against pirates on ships etc.
Published – October 10, 2025 04:44 pm IST