Last updated on September 7th, 2023 at 07:09 pm
Different uses of sound waves
Following are the various uses sound waves
1. Geologists use the knowledge of sound waves to locate the oil reservoirs inside the earth’s surface.
2. Earthquakes can be detected by the waves traveling through different kinds of rocks.
3. Sound waves are used in sonar, which can explore the sea bed and the entire sea.
4. Bats uses sonar waves to detect the obstacles in their path.
5. Sound waves obey the rules of reflection so they produce an echo. Echoes are used in medical fields.
6. Ultrasonic sounds are used for examining prenatal scanning.
7. Ultrasonic waves can be used to sterilize delicate and costly instruments. In this process, the instrument is suspended in the liquid and the ultrasonic waves pass through the liquid, which makes the liquid particles in high-frequency vibrations so that the surface of the the instrument gets cleaned.
8. Ultrasonic waves are used to detect the flaws and cracks in the metal sheets.
9. Sound waves are used to remove the congestion in the lungs. There is a simple medical instrument called lung flute, which breaks up mucus in the chest cavity.
10. Sound waves escaping from the Sun’s interior surface create lot of hot gases, which power the chromospheres.
11. Ultrasonic waves are used in diagnostic sonography, in which we can detect the body structures and the internal organs of the human body. We can detect tumors by use of ultrasonic waves.
Define reverberation, reverberation time, absorption of sound waves and co-efficient of absorption
Reverberation and Reverberation Time
The persistence of audible sound even after the source has ceased emitting sound is called reverberation.
If the reverberation of a sound pulse persists so long as to prolong the sound while several successive pulses are produced, the intelligibility will suffer, leading to poor acoustic conditions.
The time required for the sound intensity (watts per square meter) to decrease by a factor of one million so that it reaches the threshold of audibility is called the ‘reverberation time’.
If the reverberation time is too short, musical notes are isolated from one another and the music is thin’. If, on the other hand, the reverberation time is too long, the sounds from earlier notes clash with the notes being played.
For a medium-sized auditorium, the reverberation time should be of the order of 1 to 2s. Symphony hall in Boston, one of the finest concert halls in the world, has a reverberation time of 1.8s when it is fully occupied.
The reverberation time depends on the
- volume of the concert hall and
- the nature of the reflecting surfaces.
The larger the volume, the longer it takes for sound traveling at approximately 345 m/sec, to traverse the distances between the reflecting walls.
When surfaces exposed to sound waves are highly absorbent, the rate of energy absorption by all surfaces quickly becomes equal to the rate of energy production by all sources, thus the reverberation time becomes smaller.
Absorption and Co-efficient of Absorption (a)
The dissipation of sound energy into other forms of energy and ultimately into heat is called the absorption of sound waves.
The main causes of the absorption of sound by a material are its porosity and flexible vibrations. When sound waves fall on flexible materials. The material is set into sound energy into heat.
vibration and the damping force comes into play which dissipates the incident acoustic intensity to that incident on it.
The absorption coefficient ‘a’ of a material is defined as the ratio of the absorbed ACOUSTIC INTENSITY TO THAT INCIDENT ON IT.
The absorption coefficient may vary from 0 (no absorption) to 1 (complete absorption). The following table gives some typical absorption coefficients of different materials.
These are average values for the audible sound range at usually being greater for higher frequencies. normal incidence. In general, the absorption coefficient varies with frequency,
What are the different types of mechanical waves? Explain in detail
There are two types of mechanical waves.
1. Transverse wave,
2. Longitudinal wave.
1. Longitudinal waves: In longitudinal waves, the medium particles vibrate in the direction of motion of waves.
For example- when one end of the spring is tied to a hook in a wall and the other end is moved forward and backward, then every turn of the spring oscillates parallel to the length of the spring and longitudinal waves travel through the spring.
Give the different uses of sound waves
A wave motion in which the particles of the medium oscillate about their mean positions in the direction of propagation of the wave is called a longitudinal wave.
Sound waves are classified as longitudinal waves. Let us now see how sound waves propagate. Take a tuning fork, vibrate it, and concentrate on the motion of one of its prongs, say prong A.
The normal position of the tuning fork and the initial condition of air particles is shown in fig 6.1(a). As the prong A moves towards the right, it compresses air particles near it, forming a compression as shown in fig (b).
Due to vibrating air layers, this compression moves forward as a disturbance. As prong A moves back to its original position, the pressure on its right decreases, thereby forming a rarefaction.
This rarefaction moves forward like compression as a disturbance. As the tuning fork goes on vibrating, waves consisting of alternate compressions and rarefactions spread in the air as shown in fig (d).
The direction of motion of the sound waves is the same as that of air particles, hence they are classified as longitudinal waves. The longitudinal waves travel in the form of compressions and rarefactions.
2. Transverse waves: In transverse waves, “medium particles vibrate in the direction perpendicular to the direction of motion of waves.”
For example, when one end of a horizontal rope is tied to a hook and the other end is moved up and down, then transverse waves travel in the rope along its length.
A wave motion, in which the particles of the medium oscillate about their mean positions at right angles to the direction of propagation of the wave, is called a transverse wave.
These waves can propagate through solids and liquids but not through gases, because gases do not possess elastic properties. Examples of these waves are:
vibrations in strings, ripples on the water’s surface, and electromagnetic waves. In a transverse wave, the particles of the medium oscillate in a direction perpendicular to the direction of propagation as shown in figure 6.2.
Particles of the medium oscillate in a direction perpendicular to the direction of propagation Figure 6.2
Thus, during their oscillations, the particles may move upwards or downwards from the plane passing through their mean positions.
The uppermost point of the wave, i.e., the position of maximum positive displacement is the crest and the lowest point, i.e. the position of maximum displacement is called the trough. Thus in a transverse wave crests and troughs appear alternatively.