Audible frequency range in urdu hindi 10th physics wallah subject chapter 11 sound
11.7 AUDIBLE FREQUENCY RANGE
We know that sound is produced by a vibrating body. A
normal human ear can hear a sound only if its frequency lies
between 20Hz and 20,000 Hz. In other words, a human ear
neither hears a sound of frequency less than 20 Hz nor a
sound of frequency more than 20,000 Hz. Different people
have different range of audibility. It also decreases with age.
Young children can hear sounds of 20, 000 Hz but old people
SUMMARY
Sound is produced by a vibrating body. It travels in the medium from one place to
another in the form of compressional waves.
Loudness is a feature of sound by which a loud and a faint sound can be distinguished.
It depends upon the amplitude, surface area and distance from the vibrating body.
Sound energy flowing per second through unit area held perpendicular to the
direction of sound waves is called the intensity of sound. bel is unit of the intensity
level of sound, where 1 bel = 10 decibels
Pitch of the sound is the characteristics of sound by which a shrill sound can be
distinguished from a grave one. It depends upon the frequency.
The characteristics of sound by which two sound waves of same loudness and pitch
are distinguished from each other is called the quality of sound.
The sounds with jarring effect on our ears are called noise and the sounds having
pleasant effect on our ears are called musical sounds.
Noise pollution has become a major issue of concern in some big cities. Any form of
sound which disturbs the normal functioning of any natural ecosystem or some
human community is the cause of noise pollution.
Noise pollution can be reduced to acceptable level by replacing the rusty noisy
machinery with environment friendly machinery and equipments, putting sound reducing barriers, or using hearing protection devices.
The technique or method used to absorb undesirable sound energy by soft and
porous surfaces is called acoustic protection. This can be done by
travels more faster: air, solid or liquid? Justify your answer.
11.3. How can you prove the mechanical nature of sound by a simple experiment?
11.4. What do you understand by the longitudinal wave? Describe the longitudinal
nature of sound waves.
11.5. Sound is a form of wave. List at least three reasons to support the idea that sound is a wave.
11.6. We know that waves manifest phenomenon of reflection, refraction and
diffraction. Does sound also manifest these characteristics?
11.7. What is the difference between the loudness and intensity of sound? Derive the
relationship between the two.
11.8. On what factors does the loudness of sound depend?
11.9. What do you mean by the term intensity level of the sound? Name and define the
unit of intensity level of sound.
11.10. What are the units of loudness? Why do we use logarithmic scale to describe the
range of the sound intensities we hear?
11.11. What is difference between frequency and pitch? Describe their relationship
graphically.
11.12. Describe the effect of change in amplitude on loudness and the effect of change in
frequency on pitch of sound.
11.13. If the pitch of sound is increased, what are the changes in the following?
a. the frequency b. the wavelength
c. the wave velocity d. the amplitude of the wave
11.14. If we clap or speak in front of a building while standing at a particular distance, we
rehear our sound after sometime. Can you explain how does this happen?
11.15. What is the audible frequency range for human ear? Does this range vary with the
age of people? Explain.
11.16. Explain that noise is a nuisance.
11.17. Describe the importance of acoustic protection.
11.18. What are the uses of ultrasound in medicine?
CONCEPTUAL QUESTIONS
11.1. Why two tin cans with a string stretched between them could be better way to
communicate than merely shouting through the air?
11.2. We can recognize persons speaking with the same loudness from their voice. How
is this possible?
11.3. You can listen to your friend round a corner, but you cannot watch him/her.
Why?
11.4. Why must the volume of a stereo in a room with wall-to-wall carp
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