Question 1 :
<p>If pitch of a sound is pleasing to our ears, the sound is:</p>

Question 4 :
State whether given statement is True or False<br/>Noise pollution can cause partial hearing impairment. <br/>

Question 6 :
In the following sentence. say 'True' and 'False'<br/>$(a)$ Sound can't travel in vacuum (T/F)<br/>$(b)$ The number of oscillations per second of a vibrating object is called its time period. (T/F)<br/>$(c)$ If the amplitude of vibration is large, sound is feeble. (T/F)<br/>$(d)$ For human ears, the audible range is 20Hz to 20,000Hz. (T/F)<br/>$(e)$ The lower the frequency of vibration, the higher is the pitch.<br/>$(f)$ Unwanted or unpleasant sound is termed as music. (T/F)<br/>$(g)$ Noise pollution may cause partial hearing impairment. (T/F)

Question 7 :
Which of the following is / are effective for preventing noise pollution?<br/>

Question 10 :
<p>Three different vibrating bodies produce three types of sounds X, Y and Z. Sounds X and Y cannot be heared by a man having normal range of hearing but sound Z can be heard easily. The sound X is used in for monitoring nuclear reactor.The sound similar to that which is produced during an earthquake before the main shock wave is generated. What type of sounds are (i) X (ii) Y, and (iii) Z?</p>

Question 11 :
Assertion: Every vibrating body is a source of sound. Reason: All sounds are audible.

Question 13 :
What is thesafelimit of sound level in dB for our ears ?

Question 15 :
In the following statements , tick (T) against those which are true , and False against those which are false :<br>Sound generate due to vibration in objects.

Question 16 :
A sound of intensity $I$ is greater by $3.0103\ dB$ from another sound of intensity $10\ nW\ c{ m }^{ -2 }$ . The absolute value of intensity of sound level $I$ in ${ Wm }^{ -2 }$ is :<br/>

Question 17 :
When a sound wave enters the ear, it sets the eardrum into oscillation, which &#160;in turn causes oscillation of 3 tiny bones in the middle ear called ossicles. This oscillation is finally transmitted to the fluid filled in inner portion of the ear termed as inner ear, the motion of the fluid disturbs hair calls within the inner ear which transmit nerve impulses to the brain with information that a sound is present. The three bones present in the middle ear are named as hammer, anvil and stirrup. Out of these the stirrup is the smallest one and this only connects the middle &#160;ear to inner ear as shown in the figure below. The area of stirrup&#160;and its extent of connection with the inner ear limits the sensitivity of the human ear. Consider a person's eat whose moving part of the eardrum has an area of about 43 mm$^{2}$ and the area of stirrup is about 3.2 mm$^{2}$. The mass of ossicles is negligible. As a result, force&#160;&#160;exerted by sound wave in air on eardrum and ossicles is same as the force exerted by ossicles on the inner ear. Consider a sound wave having maximum pressure fluctuation of $3\times10^{-2}$&#160;Pa from its normal equilibrium pressure value which is wqual to $10^{5}$ Pa. Frequency of sound wave is 1200 Hz.&#160;<br/>Data: Velocity of sound wave in air is &#160;332 m/s. Velocity of sound wave in fluid (present in inner ear) is 1500 m/s. Bulk modulus of air is $1.42\times10^{5}$ Pa. Bulk modulus of fluid is $2.18\times10^{9}$ Pa.<br/><br/><br/>Find the pressure amplitude of given sound wave in the fluid of inner ear.&#160;

Question 18 :
A wave moves at a constant speed along a stretched string.<br>Mark the incorrect statement out of the following