Intensity and Loudness of Sound

Loudness of sound coming from a point source at a distance $R$ is $50\mathrm{dB}$. If the distance is doubled then the new loudness value will become approximately.

Which of the following equations does not represent a progressive wave?

Equation of a longitudinal wave is given as $s={10}^{-2}\sin 2\pi \left(1000t+\frac{50x}{17}\right)$(all SI units). Find the location $x$ (in $\mathrm{m}$), at $t=0$, where the magnitude of the change in pressure is maximum.

A sound level meter placed in front of the loudspeaker of a $60 \mathrm{W}$ and audio system reads $70 dB.$ All else being equal, when placed in front of $120 \mathrm{W}$ system, the meter will read ('x' in dB). Write $\frac{x+7}{10}$ as your answer. (x is in nearest integer and ${\log }_{10}2=0.30$ ).

Select the loudness of whisper.

If two sound waves, $y_1=0.3\sin 596\pi \left[t-\frac{x}{330}\right]$ and $y_2=0.5\sin 604\pi \left[t-\frac{x}{330}\right]$ are superimposed, the ratio of maximum and minimum intensities of beats is?

A sound source emits sound waves in a uniform medium. If the energy density is $E$ and the maximum speed of the particles of the medium is $v_{\max }$. The plot between $E$ and $v_{\max }$ is best represented by

If pressure amplitude in a sound wave is changed from $P_o$ to $3P_o$. The percentage increase in the intensity of wave is

Select the correct statment about the two mechanical waves, $y_1=2 \sin 2\mathrm{\pi } \left(50\mathrm{t}-2\mathrm{x}\right)$ and $y_2=4\sin 2\mathrm{\pi } \left(\mathrm{ax} +100 \mathrm{t}\right)$, propagate in a medium with the same speed. 

A displacement versus time graph ($s$-$t$graph) is as shown for particles at $x=0$, for a sound wave which is propagating towards left. (negative $x$-axis)

If $P$ is change in pressure, then choose correct matching of the graphs.

How much intense is $80 dB$ sound in comparison to $40 dB?$

The power of sound from the speaker of radio is $10 \mathrm{W}$. Now, the power of sound from the speaker of the radio is increased to $400 \mathrm{W}$ by increasing the volume of the radio. The power increased in $\mathrm{dB}$ as compared to original power is nearly

A hearing test is conducted on an aged person. It is found that her threshold of hearing is $20 \mathrm{dB}$ at $1 \mathrm{kHz}$, and it rises linearly with frequency to, $60 \mathrm{dB}$ at, $9 \mathrm{kHz}$. The minimum intensity of sound that the person can hear at, $5 \mathrm{kHz}$ is,

The intensity of sound during the festival season increased by, $100$ times. This could imply a decibel level rise from-

If the intensity is increased by a factor of $20$, then how many decibels in the sound level increased?

Displacement - time graphs for two waves, wave - $1$ and wave - $2$ are shown here. The ratio of the intensity of wave - $1$ to that of wave - $2$ is

If the amplitude of sound is doubled and the frequency is reduced to one fourth, the intensity of sound at the same point will be

A small speaker has a capacity of power $3 \mathrm{W}$. A microphone is placed at distance $2 \mathrm{m}$ from the speaker. Find the displacement amplitude of particles of air near the microphone. The frequency of sound emitted by the speaker is $1 \mathrm{kHz}$. (Density of air = $1.2 \mathrm{kg} {\mathrm{m}}^{-3}$ and speed of sound in air = $330 \mathrm{m} {\mathrm{s}}^{-1}$ )

Two loudspeakers are being compared. One is perceived to be $32$ times louder than the other. The difference in intensity levels between the two, when measured in decibels, is

(Note: Human mind perceives doubling of loudness for each $10 \mathrm{dB}$ change)

The intensity ratio of two waves is $1:9$. The ratio of their amplitudes is___