CHAPTER # 11
SOUND
Multiple Choice Questions
i. The Sound wave is an example of a longitudinal wave.ii. Sound travel from source to ear by changing air pressure.
iii. Mechanical energy.
iv. A Sound wave cannot travel in space.
v. Amplitude.
vi. 20Hz to 20kHz
vii. Wavelength and period will decrease when the frequency of sound waves increases.
REVIEW QUESTIONS
11.1 Necessary conditions for the production of sound.
The creation of sound requires both a material medium and a vibrating body because when a body vibrates, the air around it vibrates as well, creating an audible sensation in our ears.
11.2 Effect of medium on the speed of sound.
The nature of the medium has an impact
on sound speed. Solids have a faster sound speed than liquids and gases do. The
distance between the particles is the cause of this. The transfer of energy
will be greater with less space. As a result, the speed will increase, just
like in solids.
Speed of sound in solids > speed of sound in liquid > speed of sound in gases
11.3 Mechanical Nature of Sound wave.
The Sound Wave Because they require a material medium for propagation, they are mechanical in nature. The bell jar apparatus experiment can demonstrate this. When the air is pumped out of the jar, it creates a vacuum, and no sound is produced, but the bell continues to ring.
11.4 Longitudinal nature of the sound wave.
A longitudinal wave produces compression and rarefaction along the direction of propagation of the wave. The longitudinal nature of sound can be demonstrated using a tuning fork and a rubber pad.
11.5 Reasons to support that sound is a wave.
i. It creates a sinusoidal shape.
ii. Transmit energy from one place to another.
iii.
It causes resonance.
11.6 Does sound manifest reflection, refraction, and diffraction?
Yes, because the sound is a wave and waves have all these properties for reflection. The echo is the best example, also sound exhibits the phenomena of reflection, refraction, and diffraction.
11.7 Relation between loudness and intensity of sound.
|
Loudness |
Intensity of sound |
|
The distinction between loud and faint
sounds can be made based on loudness. |
The amount of sound energy that
travels per second through a unit area held perpendicular to the direction of
propagation is known as the intensity of sound. |
For derivation refer to page # 24 of the book.
11.8 On what factors does the loudness of sound depend?
1.
The amplitude of the vibrating body.
2.
Area of vibrating body.
3.
Distance from vibrating body.
11.9 What do you mean by the term intensity level of the sound? Name and define the unit of the intensity level of sound.
The intensity level of sound is defined as the difference between the loudness of L and Lo. The unit of sound intensity level is bel, but this unit is very large, so we use decibel (dB). The decibel scale is a scale construct used to measure the intensity level of sound.
11.10 What are the units of loudness? Why do we use a logarithmic scale to describe the range of the sound intensities we hear?
The unit of loudness is the bel or decibel (dB). We use a logarithmic scale to describe the range of sound intensities because the hearing range is so large that a linear scale would be inconvenient.
11.11 What is the difference between frequency and pitch? Describe their relationship graphically.
|
Frequency |
Pitch |
|
The frequency of a point is the number of waves that
pass through it in one second. |
Pitch is a
sound characteristic that distinguishes between shrill and grave sounds. |
|
Graphical Relation  |
|
11.12 Describe the effect of change in amplitude on loudness and the effect of change in frequency on the pitch of the sound.
- Loudness and amplitude have a direct relationship; the greater the amplitude, the louder the sound, and vice versa.
- Pitch and frequency are also related; higher pitch equals higher frequency and vice versa.
11.13 If the pitch of the sound is increased, what are the changes in the following?
- Pitch and frequency have direct relation. So, frequency increases.
- Pitch and wave velocity have direct relation. So, velocity will increase.
- Pitch and wavelength have an inverse relation. So, the wavelength will decrease.
- Pitch and amplitude do not have any relation.
11.14 If we clap or speak in front of a building while standing at a particular distance, we rehearse our sound after some time. Can you explain how this happens?
The sound we hear again after a while is known as an echo, and it is caused by the reflection of sound waves from the surface of a building.
11.15 What is the audible frequency range for the human ear? Does this range vary with the age of people? Explain.
The audible frequency range is the range of frequencies that a normal human ear can hear. It ranges from 20Hz to 2000Hz. It decreases as people's ages increase. For example, elderly people cannot hear frequencies above 15000Hz.
11.16 Explain that noise is a nuisance.
A noise nuisance is defined as excessive and unreasonable noise from a neighboring property. The nuisance could be coming from residential, industrial, or commercial property and has a significant impact on you and your life, making it more than just an annoyance.
11.17 Describe the importance of acoustic protection.
Acoustics protection can help employees work in a safer and more productive environment by creating a more comfortable soundscape. Rather than attempting to impose a silent workplace, acoustic protection helps manage noise levels and reduce background noise.
11.18 What are the uses of ultrasound in medicine?
- Used to diagnose and treat ailments.
- Used to remove blood clots.
CONCEPTUAL QUESTIONS
11.1 Why two tin cans with a string stretched between them could be a better way to communicate than merely shouting through the air?
This is because sound travels faster in solids than in gases (air).
11.2 We can recognize persons speaking with the same loudness from their voices. How is this possible?
We can identify them because of the sound quality, which distinguishes between similar loudness and pitch.
11.3 You can listen to your friend round a corner, but you cannot watch him/her. Why?
Due to the diffraction of sound waves, we can hear what our friend is saying but cannot see what is happening.
11.4 Why must the volume of a stereo in a room with wall-to-wall carpet be tuned higher than in a room with a wooden floor?
We all know that soft, porous, or rough surfaces absorb sound
more effectively than flat surfaces, which tend to reflect sound waves more.
The volume in a room with carpet is therefore higher than in a room with a
wooden floor.
11.5 A student says that the two terms speed and frequency of the wave refer to the same thing. What is your response?
No, the two terms are distinct. Speed is the distance traveled in a unit of time, and frequency is the number of waves that pass through a point in a second.
11.6 Two people are listening to the same music at the same distance. They disagree on its loudness. Explain how this could happen.
The reason for this is that the loudness is also affected by the physical conditions of the ear. That is why they are conscious of their loudness.
11.7 Is there any difference between echo and reflection of sound? Explain.
There is a distinction between echo and reflection. Echo is caused by the reflection of sound from smooth, nonporous surfaces; however, reflection can occur through porous surfaces in a lesser amount but cannot produce an echo.
11.8 Will two separate 50 dB sounds together constitute a 100 dB sound? Explain.
Yes, two separate 50 dB sounds added together equal a 100 dB sound. If they have the same loudness and wavelength.
11.9 Why ultrasound is useful in the medical field?
Because of its higher frequency and shorter
wavelength, ultrasound is used in the medical field. As a result, it carries
more energy.
0 Comments