Latest CBSE syllabus topics –
Sound – Nature of sound and its propagation through different media, speed of sound, range of hearing in humans; ultrasound; reflection of sound; echo and SONAR
Structure of the Human Ear. (Auditory aspect).
Latest Maharashtra SSC Board syllabus topics –
Sound – Nature of sound and its propagation through different media, speed of sound, range of hearing in humans; ultrasound; reflection of sound; echo and SONAR
Structure of the Human Ear. (Auditory aspect).
Summary –
- Sound – It is mechanical energy or vibrations transmitted through an elastic solid or a liquid or gas medium, with frequencies in the approximate range of 20 to 20,000 hertz, capable of being detected by human organs of hearing.
- Sound is produced by vibrating objects such as air, string, diaphragm etc.
- Sound only propagates through a medium from the point of generation to the listener.: no medium, no sound. i.e. In space no one can hear you scream.
- Compression – Condensed region (or region of high pressure) of the medium through which a longitudinal wave travels.
- Rarefaction – Rarefied region, or region of lessened pressure, of the medium throughout which a longitudinal wave travels.
- Sound wave which propagates as compressions and rarefactions is a longitudinal wave.
- Longitudinal Wave – A wave in which the individual particles of a medium vibrate back and forth in the direction in which the wave travels. (Sound)
- Transverse Wave – A wave in which the individual particles of a medium vibrate from side to side perpendicularly to the direction (up and down about their mean position e.g. sound) in which the wave travels. Light is a transverse wave.
- Wavelength (λ) – The distance between two consecutive compressions (C) or two consecutive rarefactions (R). Its SI unit is metre (m).
- Oscillation – The change in density from the maximum value to the minimum value, again to the maximum value makes one oscillation.
- Frequency of the sound wave (ν) – The number of oscillations per unit time. Its SI unit is hertz (hz).
- Time period of the sound wave (T) – Time taken for one complete oscillation. Its SI unit is second.
ν = 1 / T - Amplitude (A) – Magnitude of maximum disturbance in the medium. The maximum displacement or distance moved by a point on a vibrating body or wave measured from its equilibrium position.
- Speed of sound – The distance which a point on a wave, such as a compression or a rarefaction, travels per unit time.
Speed = wave length x frequency
- The speed of sound increases with increase in temperature and humidity. It is 331 m/sec in air at 0°C and it increases by 0.61 m for 1°C increase.
- Intensity of sound – The amount of sound energy passing each second through unit area i.e. energy passing through 1m² in 1 sec.
- Loudness – It is a measure of the response of the ear to the sound.
- The loudness or softness of a sound depends on its amplitude.
- Tone – A sound of single frequency.
- Note – The sound which is produced due to a mixture of several frequencies and is pleasant to listen to.
- Pitch – Highness or lowness of sound characterized by the frequency producing it.
- Timbre – The distinctive quality of tone of a sound. It enables us to distinguish a sound from another of same pitch and loudness.
- Sound waves having frequency between 20 hz to 20,000 hz is called sonic sound.
- Echo – Repetition of a sound by reflection of sound waves from a surface. To hear one’s own echo the sound producer should stand at a minimum of 17.2m from the reflecting surface.
- Reverberation – Re-echoed sound.
- Infrasonic or Infrasound – A sound frequency too low to be heard by the normal human ear. i.e. below 20Hz.
- Ultrasonic or Ultrasound– A sound frequency to high to be heard by the normal human ear. i.e. about 20kHz.
- Sonar – It is a device that uses ultrasonic waves to measures the distance, direction and speed of underwater objects.
Read Next –
Production of Sound and Propagation of Sound