Effect of Pressure on Speed of Sound in Gases

Q.

What is the effect of pressure on the speed of sound in air.

Q. State Newton's formula for the velocity of sound in a gas. What is the Laplace's correction? $\left[8\text{marks}\right]$

Q. At a pressure of $24\times {10}^{5}dyne/c{m}^2$, the volume of $O_2$ is $10$ litre and mass is $20gm$. The 'rms' velocity will be (in m/sec).

1. $800$
2. $400$
3. $600$
4. $200$

Q. The velocity of sound in air at ${15}^{0}C$ is $v_1$. If the temperature (on the absolute scale) is doubled and the pressure halved, the velocity is $v_2$. Then $v_1:v_2$ is:

1. $1:1$
   
2. $1:2$
   
3. $\sqrt{2}:1$
4. $1:\sqrt{2}$

Q. Show the derivation of the formula - Velocity of the sound =sqrt(aP/D). Whereas a the specific heat P is the pressure. D is the density or molecular inertia.

Q. How is the speed of sound in air affected by pressure of air?

1. no effect
2. decreases with the increase in pressure
3. data insufficient
4. increases with the increase in pressure

Q. If the density of water increases, the speed of sound travelling through the water decreases.

1. True
2. False

Q. In air, the speed of sound is more as compared to speed of light.

1. True
2. False

Q. The velocity of sound at ${15}^{\circ }C$ and 380 mm pressure is 340 m/s. If the temperature remains constant and pressure is doubled, the velocity of sound will be

1. 340 m/s
2. 170 m/s
3. 680 m/s
4. None of these

Q. When we clap our hands, the sound produced is best described by Hence $p$ denotes the change in pressure from the equilibrium value.

1. $p=p_0\sin (kx-\omega t)$
2. $p=p_0\cos kx\sin \omega t$
3. $p=p_0\sin kx\cos \omega t$
4. $p=\sum p_{on}\sin (k_{n}x-{\omega }_{n}t)$

Q. The pressure variations in the propagation of sound waves are

1. Isobaric
2. Adiabatic
3. Isochoric
4. Isobaric and isochoric
5. Isothermal

Q. Due to a point isotropic sonic source, loudness at a point is L = 60 dB. If density of air is $\rho =\left(\frac{15}{11}\right)kg/m^3$ and velocity of sound in air is v = 330 m/s, the pressure oscillation amplitude at the point of observation is $[I_0={10}^{-12}W/m^2]$

1. 
2. 
3. 
4. 

Q. The velocity of sound in a tube containing air at ${27}^{o}C$ and a pressure of $76cm$ of mercury is $330m{s}^{-1}$. What will be its velocity, when the pressure is increased to $100cm$ of mercury and the temperature is kept constant?

Q. Calculate the difference in the speeds (in metres per second)of sound in air $-3^{\circ }C$, 60 cm pressure of mercury and ${30}^{\circ }C$, 75 cm pressure of mercury. The speed of sound in air at $0^{\circ }C$ is 332 m/s.

Q. The pressure in a traveling sound wave is given by the equation
$\Delta p=\left(1.50Pa\right)\sin \pi [\left(0.900m^{-1}\right)x-\left(315s^{-1}\right)t]$.
Find the (a) pressure amplitude, (b) frequency, (c) wavelength, and (d) speed of the wave.

Q. The velocity of sound at 15 C and $380mm$ pressure is $340$ metres per second. If the temperature remains constant and pressure is doubled, the velocity of sound will be:

1. $340metres/sec$
2. $170metres/sec$
3. $680metres/sec$
4. None of the above

Q. Assertion :The decrease in speed of sound at high altitudes is due of fall in pressure at this altitude. Reason: The speed of sound is the same at all pressures and varies with temperature only.

1. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
2. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
3. Assertion is incorrect but Reason is correct
4. Both Assertion and Reason are incorrect

Q. Velocity of sound in air is

1. Directly proportional to the pressure
2. Directly proportional to temperature
3. Faster in dry air than in moist air
4. Independent of the pressure of air

Q. The velocity of sound in dry air at $0^{\circ }C$ and 74 cm pressure is $332m{s}^{-1}$ then the velocity of sound at ${50}^{\circ }C$ and 77.5 cm pressure in $m{s}^{-1}$ will be

1. 361.1
2. 322.7
3. 347.1
4. 352.4

Q. A certain sound source is increased in sound level by 30.0 dB. By what multiple is (a) its intensity increased and (b) its pressure amplitude increased?

Q. The velocity of sound in dry air at $0^0$C and at $74cm$ of Hg pressure is $332m{s}^{-1}$ . Then, the velocity of sound (in $m{s}^{-1}$) at ${50}^0$C and at $77.5cm$ of Hg pressure will be

1. $322.7$
   
2. $361.1$
   
3. $352.4$
   
4. $347.1$