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The number of oscillations per second is called Frequency of oscillation.

Above 80 dB it becomes painful.

Causes of sound pollution: 

1. Sounds of traffic 

2. Sounds by motor bikes and their horns 

3. Sounds in construction sites 

4. Sounds at industries 

5. Sounds at mines 

6. Sounds during explosions and bursting of crackers 

7. Sounds from mixer / grinder, washing machines and motors etc.

The steps to reduce sound pollution :

1. Attach silencers to the bikes and other machines to reduce sound. 

2. Manufacture machines that work with lesser noise. 

3. During the use of TVs and taperecorders tune down volume of sound. 

4. Plant trees to reduce sound pollution.

Above 80 dB the sound becomes physically painful.

Human can hear sound in the range of 20-20,000 Hz.

The unit of loudness of sound is decibel (dB).

Sounds of frequency higher than 20 kHz are known as ultrasonic sounds.

The amplitude of vibration is large, Sound produced is loud.

Amplitude is defined as the loudness of sound. When the amplitude is large the sound produced is large and if the amplitude is small then the sound produced is also small.

1. Vocal cords 

2. Lips

3. Teeth and tongue 

4. Nose and throat

The maximum displacement of vibrating body from its mean position is called amplitude.

The intensity of sound is proportional to the square of the amplitude of vibration. For example, if the amplitude is doubled the intensity becomes four times as much.

Drums, tabla, calling bell, school bell, etc.

We cannot produce sound without vibration in the body.

The to and fro motion of a body from its mean position is known as vibration.

It is 10¹² times more powerful than a smallest audible sound.

Decibel is the unit used to measure the sound level

Correct option is  A) 0

(Upto 120 dB).

Correct option is C) 120 dB

A) 50 dB to 60 dB

Correct Answer is: (b) A = 1 mm , (c) The smallest length of the string is 50 cm.

Comparing with the equation y = 2Asin (nπx/L) cos(ωt)

2A = 2 mm

or A = 1 mm

nπx/L = 6.28x = 2πx

or L = n/2 m. 

For n = 1, L = 0.5 m.

Correct Answer is: (d) 4 V

Frequency = V/(L/2) = 2V/L = 1/2L (v),

where v = the velocity of transverse waves on the string.

Two factors on which the speed of a wave travelling in a medium depends are:

(i) Density: The speed of sound is inversely proportional to the square root of density of the gas.

(ii) Temperature: The speed of sound increases with the increase in temperature.

Correct Answers is: (a, b, c, & d)

(i) Wavelength (or speed) of the wave changes, when it passes from one medium to another medium.

(ii) Frequency of a wave does not change when it passes from one medium to another medium.

Correct Answer is: (a) ϕ = π , (d) Δ = 5 x 10 ^-5 m

λ = 300m/s / 25 Hz = 12m.

Separation between A and B = 6 m = λ/2.

Correct Answer is: (a, b, & d)

The electrocardiogram (ECG) is one of the simplest and oldest cardiac investigations available. In ECG, the sound variations produced by heart is converted into electric signals. Thus an ECG is simply a representation of the electrical activity of the heart muscle as it changes with time. Usually it is printed on paper for easy analysis. The sum of this electrical activity, when amplified and recorded for just a few seconds is known as an ECG

The intensity of sound heard at a place depends on the following factors;

1. Amplitude of the source 

2. Distance of the observer 

3. Surface area of the source 

4. Density of the medium 

5. Frequency of the source.

Sound travels about 5 times faster in water than in air. Therefore, two whales in the sea, hundreds of kilometers apart can communicate easily.

Distance (d) = velocity (v) × time (t) 

Distance travelled by sound when gun fires first time, 2d = v × 5 ……(1) 

Distance travelled by sound when gun fires second time, 2d – 620 = v × 3 …….(2) 

Rewriting equation (2) as, 

2d = (v × 3) + 620 ………(3) 

Equating (1) and (3), 5v = 3v + 620 

2v = 620 .

Velocity of sound, v = 310 m s^-1

Sound is a form of energy which produces the sensation of hearing. It is produced due to vibrations of different objects, eg. stretched vibrating wires and vibrating drums, etc.

λ = v/n

Here, v = 344 m s^-1 

n = 22 MHz = 22 × 10⁶ Hz

λ = \(\frac{344}{22}\)× 10⁶ = 15.64 x 10⁶ m = 15.64 µm.

As the vibration of the particles of the medium are along the direction of wave propagation, sound waves are longitudinal waves

Sound waves are called longitudinal wave because the particles do not move from one place to another but they simply oscillate back and forth about their position of rest.

The vibration of the medium that travels along or parallel to the direction of the wave is called a longitudinal wave. In a sound wave, the particles of the medium vibrate in the direction parallel to the direction of the propagation of disturbance. Hence, a sound wave is called a longitudinal wave.

In a longitudinal wave, the individual particles of the medium move in a direction parallel to the direction of propagation of the disturbance. The particles oscillate back and forth on their position of rest. A sound wave propagates in the same way. So, they are called longitudinal waves.

Given 

Speed of sound (u) = 342 m/s 

Time taken for hearing the echo (t) = 6 s 

Now

speed= \(\frac{distance}{time}\) 

⇒ 342 =\(\frac{distance}{6}\)  

⇒ Distance travelled by the sound = 342 ×6 = 2052 m.

In 6s, sound has to travel twice the distance between the source and reflecting surface. Therefore, the distance of the reflecting surface from the source =\(\frac{2052}{2}\) = 1026 m

Distance of reflecting surface = 1026 m.