Important questions based on NCERT syllabus for Chapter 13 - Sound:
Question-1: What are audible and inaudible sounds? What is the audibility frequency range for human ear?
Solution: 1. Sounds of frequencies less than about 20 vibrations per second(20 Hz) cannot be detected by the human ear(infra sonics). On the higher side, sounds of frequencies higher than about 20,000 vibrations per second (20 kHz) are also not audible to the human ear(ultra sonic). Such sounds are called inaudible.
2. The frequencies between 20 Hz and 20000 Hz are audible sounds.
3. Thus, for human ear, the range of audible frequencies is roughly from 20 to 20,000 Hz.
Question-2: How can the noise pollution be controlled in a residential area?
Solution: 1. The noisy operations must be conducted away from any residential area.
2. Noise producing industries should be set up away from such area.
3. Use of automobile horns to be minimized.
4. TV and music systems should be run at lower volumes.
5. Plants must be planted along the roads and around buildings to minimize the harmful effects of noise pollution.
Question-3: Write 5 valid points on hearing impairment.
Solution: 1. The total hearing impairment, which is rare, is usually from birth itself.
2. Partial disability is generally the result of a disease, injury or age. Children with impaired hearing need special care.
3. By learning sign language, such children can communicate effectively. Because speech develops as the direct result of hearing, a child with a hearing loss may have defective speech also.
4. Technological devices for the hearing-impaired have made it possible for such persons to improve their quality of life.
5. Society can do much to improve the living environment for the hearing-impaired and help them live normal lives.