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Sound and hearing

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Sound and hearing

  1. 1. SOUND AND HEARING
  2. 2. PRODUCTION OF SOUND1. Sound is a form of energy that moves in the form of waves.2. Vibrations of objects produce sound.3. Vibrating object transfer the kinetic energy to air molecules around them. The vibrations of the air molecules are detected by our eardrum as sound.4. Different vibrations produce different types of sounds.
  3. 3. Transmission of SoundSound needs a material or medium to travel.a) Sound can travel through solids, liquids and gases.b) Sound cannot be transferred through a vacuum, because it does not have any particles.Sound travels at different speeds in differentmedium. Sound moves fastest in solid becausethe particles are arranged very close to eachother.Sound moves slowest in gases because theparticles are very far away from each other.
  4. 4. Properties of Sound Sound can be absorbed and reflected when it hits a surface. Sound energy can be reflected or absorbed by the surface of an object. When sound reaches the surface of a solid, some waves are reflected, while some are absorbed. Absorption of sound makes the reflected sound weaker than the original sound.
  5. 5. Properties of SoundThe intensity of the reflected sounddepends on the amount of sound energyreflected or absorbed by the surface. Whenmore sound energy is reflected, the soundis louder.The intensity of sound reflected dependson the nature of the surfaceHard, even and smooth surfaces like plank,concrete and metal are good soundreflectors.Surfaces that are soft and rough like cloth,carpet and cushion are good soundabsorbers.
  6. 6. ECHO When sound is reflected repeatedly from one surface, an echo is produced. Echo produces two different types of sound, i.e the original and the reflected sound. Both of them can be heard separately. Echo occurs in enclosed places like caves, tunnels and halls. Echo cannot be heard in a small room because the reflected sound overlaps the original sound. When an echo is produced, we cannot hear the sound clearly. Echo and be reduced by putting curtains, carpets and soft cushions.
  7. 7. Pitch and Frequency 1. Frequency of a sound is the number of vibrations in one second. It is measured in hertz (Hz). 1 hertz (Hz) = 1 vibration per second The degree of highness or lowness of a sound is known as the pitch. The pitch of sound depends on the frequency. The higher the frequency, the higher is the pitch. Therefore, a higher frequency produces a high-pitched sound.
  8. 8. Pitch and FrequencyThe pitch of a sound produced by avibrating string depends on the;- Length of the string A shorter string vibrates faster to produce a higher pitch- Tension of the string A higher pitch is produced by a more stretched tight string , this makes the sound sharper- Thickness of the string A thinner string produces a higher pitch
  9. 9. Hearing Defect and Ways toRectify Them Hearing defect occur when the sense of hearing does not function properly There are different kinds of hearing defect. To understand the nature of the defect, we need to identify the part of the ear that is affected The earwax in the auditory canal can block sound waves and causes temporary loss of hearing
  10. 10. Hearing Defect and Ways toRectify ThemThe ossicles in the middle ear may be fusedtogether as a result of an infection. This preventsthe ossicles from moving freely. If this conditions isnot treated immediately, it will result in a totalhearing loss.The inner ear may be damaged by local infections.Toxins are produced as a result of diphtheria orscarlet fever. These toxins damage the cochleaand cause loss of hearingThe sensory cells in the cochlea may bedamaged by exposure to loud sounds. This cancause hearing loss.
  11. 11. Correcting HearingDefectsProgress made in science andtechnology has enabled us to correcthearing problems.Ears, nose and throat specialists mayuse syringes and warm water toremove the wax which is blockingthe auditory canals.Fused or damaged ossicles can bereplaced by surgery
  12. 12. Correcting HearingDefects Punctured eardrums can also be repaired by surgery. Damaged eardrums can be repaired or replaced by using membranes from other parts of the body. Electronic gadgets can be implanted into the ears to help some deaf people to hear better
  13. 13. Limitation of Hearing The human ear has the ability to detect sounds in the frequency range of 20 Hz (hertz) to 20 000 Hz. Humans cannot hear very low frequency or very high frequency sounds.
  14. 14. Limitation of Hearing The range of hearing varies from one individual to another.(a) Children have eardrums that are more elastic. They hear better(b) As people age, their hearing worsens. Their eardrums become less elastic. The range of sound frequencies that they can detect becomes narrower. Their ability to hear high- pitched sounds decreases.(c) A person exposed to constant loud noises experiences loss of hearing . His range of hearing is less than that of a normal person.(d) Frequencies exceeding 20 000 Hz are called ultrasonic frequencies. However , some animals can.
  15. 15. Organism Range of sound frequencies (Hz)Human being 20-20 000Whale 10 – 20Dog 67 – 45 000Frog 50 – 10 000Cat 45 – 65 000Snake 100 - 800Bat 2000 – 120 000Dolphin 1000 – 120 000grasshopper 100 – 15 000
  16. 16. Ways to overcome Our Hearing Limitations Devices FunctionsAmplifier To amplify weak sound signalsStethoscope Helps doctors to detect soft sounds like heartbeats of their patientsLoudspeaker - To make announcements during school assemblies in the school fields or school hallEarphone - Converts electrical waves into sound waves, so that they can be detected by the ears. - Enables us to hear something specific without disturbances from the noises around us

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