Sound waves
A sound is a form of energy and it produces the sensation of hearing. It is produced due to mechanical vibrations and propagates as a longitudinal wave with alternate compressions and rarefactions. Sound waves travel through solids, liquids and gases. Their speed varies depending on the properties of the medium.
The human ear is sensitive to sound waves of frequency between 20 Hz to 20,000 Hz. These waves are known as audible waves. The sound waves having a frequency below the audible range is called the infrasonic waves. Sound waves having a frequency above the audible range is called ultrasonic sound waves.
Properties of Sound Waves
- Sound is the energy that produces the sensation of hearing.
- Sound waves require a material medium for propagation
- Sound waves travel in the form of longitudinal waves. They can travel through solids as transverse waves.
- The sound waves travel at different speeds in different mediums. The speed of sound in a medium depends on the elastic property and the density of the medium
- Sound waves undergo reflection and refraction.
- When the sound waves travel from one medium to another there is a change in the velocity and the wavelength of the wave. The frequency of the wave remains constant.
- Sounds waves exhibit interference and diffraction.
- When sound waves are incident on the surface the surface vibrates.
Newton’s Formula for speed of sound
Newton showed that the speed of sound in any medium is given by the formula
v=√E/ρ
E is the modulus of elasticity
ρ is the density of the medium
Factors Affecting the Speed of Sound in Gases
The speed of sound in a gas is directly proportional to the square root of the absolute temperature. The speed of sound is independent of the pressure provided the temperature remains constant.
Can sound waves travel in a vacuum?
We know that sound waves are produced by mechanical vibrations. So, can sound waves travel in a vacuum? The answer is NO!!. Sound waves cannot travel in the vacuum. They require a material medium for their propagation.
Noise and Music Sound
Audible sounds can be classified as noise and music. A sound that produces an unpleasant effect on our mind is called noise. The sound that produces a pleasant sound is called music.
Characteristics of a Musical Sound
The following are the characteristics of a musical sound
Pitch
The pitch of the sound depends on the fundamental frequency of the note. Pitch is that characteristic that helps us distinguish between sharp sound and dull sound. The voice of a lady generally has a higher pitch compared to men’s voice.
Intensity
The intensity of sound at a point in a medium is the average rate of transfer of energy per unit area, the area being perpendicular to the direction of propagation of sound.
Quality or timbre
Quality is that characteristic of a musical sound by virtue of which it can be distinguished from another musical sound of the same pitch and intensity.
