Sound

• Define sound

  A sound is a form of energy which produces a sensation of hearing
• state the speed of sound in iron, water and air


  iron - 5000, water - 1500 and air 330
• when a layer of air moves forward it creates a space of very ___ pressure


  low
• Define longitudinal wave

  The wave in which the particles of the medium vibrate about their mean positions in the direction of propagation of sound is called longitudinal wave
• Define Amplitude

  The maximum displacement of a particle in a medium on either side of its mean position is called the amplitude of the wave
• Define time period

  Time taken by a particle of a medium to complete one vibration is called the time period
• Define frequency

  The number of waves passing through a point in one second
• What is the symbol frequency

  Hertz (Hz)
• Each source of sound is a ________ ____

  vibrating body
• Define Wave

  The periodic disturbance produced in a medium is called a wave
• Sound is a form of energy. Give reason

  When a body vibrates, the particles of the medium also start vibrating. During vibrations, the kinetic energy changes into potential energy and potential energy changes into kinetic energy. Hence, sound is a form of energy
• Is a sound wave a mechanical wave? Give reason

  Yes, sound wave is a mechanical wave because just like the other mechanical waves, sound requires a medium to travel
• Define Rarefaction

  The low pressure area created during propagation of sound is called as rarefaction
• Define Compression

  The high pressure area created during the propagation of sound is called as compression
• When the rarefaction moves forward why do air layers near the strip return to their normal position?

  Due to the elasticity of the medium
• _________ and ________ regions carry the disturbance forward

  compression and rarefaction
• Compression and rarefaction regions have a ________ speed depending on the ______ __ ___ ______

  definite

  nature of the medium
• Sound travels in the air in the form of __________ waves which can be produced in solids, liquids as well as in gases

  longitudinal
• Explain the process of propagation of wave in a medium

  In the propagation of a wave in a medium the particles, vibrate about their mean positions (without leaving the positions) and they transfer energy at a constant speed from one place to the other
• State some characteristics of frequency of a wave

  It is equal to the frequency of vibrations from its source. It is the characteristic of the source, which produces the sound. It does not depend on the nature of the medium, amplitude of vibration through which the ray propagates
• FREQUENCY=1/TIME PERIOD
• The distance travelled by a medium in one time period of vibration of particle of medium is called the wavelength

  Represented using lambda
• AMPLITUDE DEPENDS ON THE NATURE OF THE MEDIUM THROUGH WHICH THE WAVE TRAVELS
• How is the wavelength taken in a longitudinal wave?

  The distance between two consecutive compressions or between two consecutive rarefactions is equal to one wavelength
• SPEED = FREQUENCY X WAVELENGTH
• Increase in temperature increases the speed of sound because particles move faster at higher temperatures.
• In a longitudinal wave

  Displacement of particles on +Y axis - Motion of medium particles in the direction of propagation of a wave

  Displacement of particle on -Y axis - Motion of particles in the direction opposite to the progation of sound
• If the particles of a medium vibrate normal to the direction of propagation of a wave, the wave is called as a "transverse wave"

  Eg - sound waves produced in strings
• Pitch depends on the _____ of the sound

  frequency
• Loudness of a sound depends on ________

  amplitude of vibration of a vibrating body

  Greater the amplitude of the vibrating body, greater is the sound produced
• A sound wave is characterized by its ______ and ________

  amplitude and frequency
• Sound travels fastest through solids and slowest through gases
• The three characteristics of a sound are loudness, pitch, and frequency. These characteristics can be known from the wave pattern of that sound
• Loudness is the characteristic of sound by virtue of which a loud sound can be distinguished from a faint sound, both having the same frequency and the same wave form
• Factors affecting the loudness of a sound are

  1. Amplitude of the wave
  2. Distance from the source of sound
  3. Surface area of the vibrating body
  4. Sensitivity of the listener
• LOUDNESS CANNOT BE MEASURED
• The energy of sound reaching an area surface in one second is called the intensity of the sound
• The intensity of sound can be measured. It does not depend on the sensitivity of the listener. However larger the intensity, the louder the sound. Thus, loudness depends on intensity
• LOUDNESS IS DIRECTLY PROPORTIONAL TO THE SQUARE OF AMPLITUDE
• The loudness is measured on a special scale called the decibel scale.