Can you imagine a place where you are not surrounded by sound? May it be soothing sound of the river or the sound at the construction sites. There would have been no fun playing music at your friends birthday party or playing a musical instrument. Sound enables us to communicate with each other. Let us study it in detail.
All of us like listening to music. What is that enables us to listen to the pleasant music of the musical instruments, the soothing sound of the shores, phone calls with your friend who is at the long distance and more such sounds? This is all possible with our ear. Human Ear enables us to listen to all the sounds in our surroundings. Let us study the ” Human Ear” in detail.
The ear is the human organ that enables us to hear sounds around us. The main function of the ear is to maintain our sense of balance and to detect the various sounds. It helps us to convert the pressure variations into electronic signals that travel through the brain with the auditory nerve.
Human ear has three parts namely,
Inner Ear
Middle Ear
Outer Ear
Whenever the sound waves enter our ear, they travel across the outer ear. Ear converts audible frequencies into electric signals that travel to the brain. The outer ear is known as pinna and earlobe which is the broad part and has shell-like structure. The compressions reaching the outer ear i.e. the pinna directs the compressions to the canal and makes them reach the eardrum or the membrane. The membrane being flexible separates the middle ear and the outer ear. These compressions are further amplified several times like about 20 times by the three bones inside the ear.
Bones are located in the middle part and are linked together to each other. Hammer, the Anvil, and the Stirrup are the three bones which transmit the sound. The center part of the eardrum is connected to the hammer. As the hammer vibrates, it transmits the sound to the other two bones, i.e. to the anvil and stirrup. These bones amplify the sound waves and all this takes place in the middle ear. So what is it that the outer ear does; it brings in the sound waves and further these waves are amplified by middle hear.
The inner ear known as Cochlea is a snail-like structure. As the number of variations is transmitted in the middle ear, cochlea sends the sound to the brain as some amount of fluid is present inside the cochlea. These electrical impulses then go to the auditory nerve. This is exactly what we perceive as sound.
Let us suppose you are standing at the height of a mountain and yell Hello!!! Within a second, you can hear your voice back echoing in the manner Hello!! Hello!! Hello!! This is what exactly echo is. It reflects back to you. Let us study this in detail.
Why do we always need a large area to see reflections? When the sounds travel through a certain medium, it strikes the surface of other medium and bounces back to its original medium that is the initial medium. This is what reflection of sound is. The only requirement for the reflection of the sound wave is that the reflecting surface must be bigger than the wavelength of the wave. Reflection of the sound wave is seen in echoes, megaphone, ear trumpet etc.
Laws of Reflection of Sound
An angle of incidence is equal to the angle of reflection.
Incident wave reflected wave and normal at the point of incidence, all lie in the same plane.
Reflection of Sound can be applied in:
Sound producing devices use a conical shape like megaphones to increase the intensity of sound waves in particular directions.
In stethoscope, sound undergoes multiple reflections in the wires of the stethoscope.
Curved ceilings of halls use soundboards to evenly distribute the sound across the hall.
Every sound is produced by the vibration. Vibration is nothing but the back and forth movement of the object. How does the sound energy travel? Do you wonder how that works? Sound energy travels in the form of sound waves. Sound waves travel in all directions. In solids, the particles are very close to the other one. Sound energy moves as one particle hit another particle. Here sound travels at a very high speed. In liquids, the particles are at a distance, so it takes more time to travel. In gas, the particles are spread out. Here the speed of the sound energy is the slowest.
Every one must have heard of the word echo. Echo is basically a sound heard after the sound is reflected back when the actual sound has stopped. Thus the echo is the result of reflection. If we want to hear an echo, we cannot do it in a small room, we need a large area. When we shout in a large or vacant space, the sound is reflected back.
Suppose you are standing in front of a high wall and clap your hand, you can hear the same sound of the clap back again. This is an echo. An echo is heard when the distance between the person producing sound and the rigid obstacle is long enough to allow the reflected sound to reach the person least 0.1 seconds after the original sound is heard. Otherwise, the echo is not distinguished even on reaching the ears. This value can be calculated and comes out to be 17.2 m for air and 70 m for water.Whenever echo is to be heard the time between two objects or body or points should be 0.1 sec.