Question:
Hearing may be damaged by excessive noise.So our ears sometimes need protection from continuous loud sound. Hearing damage depends on the sound intensity level (decibel level)and the exposure time,and the exact combinations vary for different people.Normally,at 90 dB,it takes 8 hours or less for the damage to receptor nerves to occur.Further,it is found that if the sound level is increased by 5 dB,the safe exposure limit is cut to half.
(a) How long will it take for a sound of a very loud lawn mower (or a motorcycle) of 95dB to damage the hearing ?
(b) What is the nonstop exposure time for a 105 dB sound to damage the ear ?
(c) What should be done to protect the society from the danger of losing the divine gift of hearing power ?
Answer:
(a) Intensity level of a lawn mower,i.e., 95 dB is 5 dB above 90 dB.Obviously,this sound takes (1/2) (8 h),i.e.,4h to damage hearing.
(b) Intensity level of 105 dB is 15 dB (i.e.,3 times 5 dB) above 90 B and as such it takes (8 h),i.e.,lh to damage the ear.
(c) Stereos and other sound systems should be played at low intensity,rock concert (110 dB) should be attended only for a small duration and that too if very essential.We should protect our ears from gunshot blasts,firecrackers and loud sporting events.Late night celebrations (Jagrans,Kirtans,Marriage functions) should be without loudspeakers as they are meant for those who are present there and not for the general public.
Sound
Q 1.
Fill in the blanks :
If a body repeats its back and forth, to and fro or up and down motion along a certain path, about a fixed point, in a certain time interval then the motion of such objects is said to be _____________.
Q 2.
What is speed of sound in air?
Q 3.
Fill in the blanks :
The principle on which stethoscope works is _____ (reflection/ multiple reflection)
Q 4.
What type of wave is represented by density- distance graph?
Q 5.
Distinguish between loudness and intensity of sound.
Q 6.
What is Sound? Why it is important for us?
Q 8.
Fill in the blanks :
In the case of ____________ wave, distance between two consecutive crests or troughs is known as wavelength.
Q 9.
What are wavelength, frequency, time period and amplitude of a sound wave?
Q 10.
What are ultrasonics?
Q 11.
What is reverberation?
Q 12.
Fill in the blanks :
RADAR (Radio Detection And Ranging) works on _____________ principle which is used to determine the velocities and movement of aircrafts.
Q 13.
Radio Ceylon broadcasts at 25 m.What is the frequency of the station ?
Q 14.
How is ultrasound used for cleaning ?
Q 15.
Why are the ceilings of concert halls curved ?
Q 16.
Cite an experiment to show that sound needs a material medium for its propagation.
Q 17.
Draw a curve showing density or pressure variations with respect to distance for a disturbance produced by sound.Mark the position of compression and rarefaction on this curve.Also define wavelengths and time period using this curve.
Q 18.
What are transverse waves ?
Q 19.
Deaf people can be made to dance to music.Explain how ?
Q 20.
Why sound waves are called mechanical waves?
Q 21.
What is infrasonic? Give an example.
Q 22.
A wave of wavelength 0-60 cm is produced in air and it travels at a speed of 300 m/s.Will it be audible ?
Q 23.
Write the name of the wave which propagates in terms of compressions and rarefactions.
Q 24.
What is audible range ?
Q 25.
How can you make a building sound proof ?
Q 26.
What is SONAR ? How is it used to detect an underwater object and measure its distance
Q 27.
Fill in the blanks :
Number of oscillations completed by the oscillator in one second is known as ___________.
Q 28.
Fill in the blanks :
In a __________ wave the particles of the medium oscillate in a direction perpendicular to the direction in which the wave propagates.
Q 29.
How are the wavelength and frequency of a sound wave related to its speed?
Q 30.
A child hears an echo from a cliff 4 s after the sound of a pwerful cracker is produced.How far away is the cliff from the child ? (Take speed of sound in air as 340 m/s)
Q 31.
An engine is approaching a hill at constant speed.When it is at a distance of 0.9 km,it blows a whisde,whose echo is heard by the driver after 5 s.If the speed of sound is 340 m/s,calculate the speed of the engine.
Q 32.
What is sound barrier ?
Q 33.
Discuss the structure of human ear from auditory aspect only.
Q 34.
Fill in the blanks :
The product of wavelength of wave and its frequency gives _____________.
Q 35.
Fill in the blanks :
Loudness of sound is measured in ___________.
Q 36.
Distinguish between loudness and intensity of sound.
Q 37.
What is sound and how is it produced ?
Q 38.
Explain how the human ear works.
Q 39.
What is acoustical transite ?
Q 41.
What is sound ? Discuss the method of its production.
Q 42.
Obtain a relation between speed,frequency and wavelength of a wave.
Q 43.
What do you mean by reverberation and reverberation time ? How is reverberation controlled ?
Q 44.
We see flash earlier than the thunder.Discuss.
Q 45.
Fill in the blanks :
If a body repeats its motion, within fix interval of time, along a certain path, about a fixed point, it is said to have ____________.
Q 46.
Fill in the blanks :
A ________ (pulse/wave) is a disturbance which is sudden and lasts for a short duration of time.
Q 47.
Fill in the blanks :
Sound, compressional waves in springs are examples of _____________.
Q 48.
Fill in the blanks :
Sound having frequency less than 20Hz is known as ___________.
Q 49.
Fill in the blanks :
The distance between two consecutive compressions or two consecutive rarefactions is called the ______________.
Q 50.
What is a mechanical wave?
