Sound and Human Ear: Introduction

Sound is one of the beautiful forms of energy that produces a sensation of hearing in our ears. In the  sound produced by different objects such as alarm clocks or drums etc,  the ear acts as the medium. And this sound is known as vibration. Through the funnel-shaped outer part of our ear the sound first enters, and it moves to the eardrum through a canal. The functioning of ear eardrums plays an important role. When the eardrums vibrate, these vibrations pass to the inner ear by following the middle air bones. The three middle ear bones vibrate when  the eardrum moves. And because of this vibration the fluid moves in the inner ear. The inner ear is known as cochlea. In this coiled shaped cochlea the fluid movement causes sensory receptors and sends a signal with the auditory nerve to the brain. And this is how we can hear.

Production of Sound

The vibration of various objects produces sound:

• Vibration can be defined as rapid to and fro movement of an entity
• The human voice generates sounds through vibration in the vocal cord

Propagation of Sound through Air

Sound is propagated through air or the other medium as a longitudinal wave. In this longitudinal wave the mechanical vibration that is constituting with the waves occurs by following the direction of the propagation of the wave. This medium can be a substance or matter. The substance can be solid, aqueous, or gaseous. It promulgates through the medium from the origin to the auditor.

Range of Hearing

• The audible scale of sound for human ears ranges from 20Hz to 20000 Hz
• Children under the age of five and some animals like dogs can hear up to 25 kHz

Ultrasound

Ultrasounds are high-frequency waves. Even in the presence of obstacles, these can propagate along distinct paths. Ultrasound has extensive use in industries as well as in medical purposes. Some of the best applications are as follows:

• Ultrasound is mainly utilized to clean parts located in inaccessible places. For example, ultrasound is used to clean electronic components, spiral tubes, etc
• Defects in metal blocks and splits can be found through ultrasound
• These are made to reflect from various parts of the heart and form the image of the heart. This technique is called echocardiography
• The images of internal organs of the human body can be obtained by using ultrasonic sound waves, which are generated by an instrument called an ultrasound scanner. These images of internal organs are then shown on a monitor or printed on a transmission. This technique is called ultrasonography
• It helps the doctor to detect abnormalities. During pregnancy, ultrasonography is used for the scanning of the fetus
• Small stones formed in the kidney can be broken into fine pieces using ultrasound
• Porpoises locate food in the dark and navigate by using ultrasound

Sonar

Sound navigation and ranging or Sonar is an instrument that uses ultrasonic waves to evaluate the speed of underwater substances and distance.

• Ultrasound is lodged in a boat or a ship which consists of a detector or a Transmitter
• The transmitter produces and transmits ultrasonic waves
• These ultrasonic waves move through the water, and when it hits the seabed, it gets reflected and is detected by the detector
• The ultrasonic waves are transformed into electrical signals by the detector
• The scope of the substance can be assessed by estimating the speed of sound in water and the time span among transmission and gathering of the ultrasound. This technique is called reverberation running
• The depth of the ocean and submerged slopes, valleys, submarines, ice sheets, submerged boats, and so on, can be distinguished and dictated by sonar procedure

Structure of Human Ear

The ear is an extremely sensitive device that enables humans to hear. It transforms pressure variations in the air with audible frequencies into electrical signals that the brain carries through the auditory nerve.

• The outer ear is called pinna. It collects the sound from the surroundings. Through the auditory canal, the assembled sound passes
• There is a thin membrane called the tympanic membrane or eardrum at the end of the auditory canal
• The eardrum or tympanic membrane is a thin membrane located at the end of the auditory canal
• When the eardrum receives compression from the medium, the pressure on the exterior of the membrane increases and pushes the eardrum inward
• When rarefaction reaches the eardrum, it again moves outward
• In this manner, the vibration of the eardrum happens, and this vibration is enhanced by three bones – hammer, anvil, and stirrup, which are found in the middle ear
• The middle ear receives the sound wave and transmits the amplified pressure difference to the inner ear
• The cochlea, present in the inner ear, converts the pressure difference into electrical signals
• Then auditory nerves transfer these signals to the brain, and the brain elucidates them as sound

Hearing Aid

People with loss of hearing need a hearing aid.

• It is an electronic, battery-operated device. A microphone is used in hearing aids to receive the sound
• The electrical signal is generated from the sound wave through the microphone. To amplify the electrical signals, an amplifier is used
• The speaker of the hearing aid gets the amplified signal
• To clear hearing, the speaker transforms the amplified signal to sound and transfers it to the ear

Conclusion

Different MCQs from this topic ‘Sound and Human Ear’ are asked in the UPSC prelims and mains. Aspirants need to do good preparation for scoring a good marks in this section. In this topic we have learnt how human beings can hear. What is the relation between sound and human ear etc. The vibration of various objects produces sound. People with loss of hearing need a hearing aid. A hearing aid  is an electronic, battery-operated device. A microphone is used in hearing aids to receive the sound