Railway Science (Physics-Sound) (Part-II)

Aluminium (6420 m/s). Sound is a mechanical wave and needs a material medium for its propagation. It cannot travel through a vacuum. Speed of sound (m/s) in different media at 25°C:- Solids - Nickel (6040), Steel (5960), Iron (5950), Brass (4700). Liquids - Sea Water (1531), Distilled Water (1498), Ethanol (1207), Methanol (1103). Gasses - Hydrogen (1284), Helium (965), Sulphur dioxide (213).

This is the perception of a sound wave reflecting off a surface and returning to the listener after a certain delay. Resonance: This occurs when the frequency of a sound wave matches the natural frequency of an object, causing the object to vibrate.

Speed of sound in different mediums at 25°C : Aluminium - 6420 m/s, Nickel - 6040 m/s, Steel - 5960 m/s, Iron - 5950 m/s, Distilled Water - 1498 m/s, Ethanol - 1207 m/s, Methanol - 1103 m/s, Hydrogen - 1284 m/s, Helium - 965 m/s, Air - 346 m/s.

Echolocation (also called sonar): This is a technique that uses sound waves to determine the distance to an object. It works by sending out a sound pulse and measuring the time it takes for the echo to return.

The speed of sound is primarily determined by the elasticity and density of the medium through which it travels. Sound travels fastest in steel, followed by water and then air. The denser the medium, the faster will be the speed of sound in that particular medium.

As sound waves are longitudinal waves, the air particles vibrate to and fro in the direction of propagation of sound. A longitudinal wave is one where all the particles of the medium (such as gas, liquid or solid) vibrate in the same direction as the wave.

Sound travels as disturbance in air as compression and rarefaction. A receiver is a device that accepts signals, such as radio waves and converts them into a useful form. Sources are objects which encode message data and transmit the information, via a channel, to one or more observers/receivers. A particle is a small portion of matter.

The pitch of the sound is directly proportional to frequency. The characteristic of sound that differentiates whether a sound is shrill or flat is known as pitch. Loudness of sound depends on amplitude of the sound waves. The higher the amplitude, the higher the loudness. The wavelengths of sound frequencies audible to the human ear (20 Hz–20 kHz).

Sound is a form of energy and is produced by vibrations of objects. Properties - Longitudinal and mechanical in nature and it requires a medium (solid, liquid or gas) to travel through. In humans, It is created by the voice box or the larynx. For the human ear, the range of audible frequencies - (20 to 20,000 Hz). Some animals like dogs can hear sounds of frequencies higher than 20,000 Hz. Measuring unit - Decibel (dB).

Sound is a vibration that propagates as an acoustic wave, through a transmission medium such as a gas, liquid or solid. They are longitudinal waves. Sound cannot travel through a vacuum as there are no particles present for vibrations to take place. It always needs a medium to travel. Sound travels slowest through gases, faster through liquids, and fastest through solids. Solids > Liquid > Gas.