All questions of Sound for Class 8 Exam

The pitch of sound depends upon the frequency of the sound by the emitting source. Greater the frequency of the sound , higher will be the pitch of that sound.

Sound waves are travelling vibrations of particles in media such as air, water or metal. ... So it stands to reason that they cannot travel through empty space, where there are no atoms or molecules to vibrate.
So answer is false .

The higher the frequency of vibration, the higher the pitch and shriller the sound. This means that sounds with higher frequencies are perceived as higher-pitched and more piercing.

By noise pollution all the organisms are distrubed so d is right option

The Frequency Determines the Shrillness or Pitch of a Sound - True

Frequency refers to the number of cycles or vibrations that occur in a sound wave in a given amount of time. It is measured in Hertz (Hz), which represents the number of cycles per second. The frequency of a sound wave directly affects its pitch or shrillness.

Frequency and Pitch
- Pitch refers to how high or low a sound is perceived to be. It is determined by the frequency of the sound wave.
- Higher frequencies are associated with higher pitches, while lower frequencies are associated with lower pitches.
- For example, a high-pitched sound, like that of a flute or a bird chirping, has a higher frequency compared to a low-pitched sound, like that of a bass guitar or a car engine.

Relation between Frequency and Pitch
- The relationship between frequency and pitch is directly proportional. As the frequency of a sound wave increases, the pitch also increases.
- This means that if the frequency of a sound wave doubles, the pitch will also double. Similarly, if the frequency is halved, the pitch will be halved as well.
- For example, if a sound wave has a frequency of 1000 Hz, it will have a higher pitch compared to a sound wave with a frequency of 500 Hz.

Shrillness and Frequency
- Shrillness refers to the perception of a sound wave as being sharp, piercing, or high-pitched.
- The higher the frequency of a sound wave, the more shrill it is perceived to be.
- This means that as the frequency of a sound wave increases, the shrillness also increases. Conversely, as the frequency decreases, the sound becomes less shrill.

Examples
- In musical instruments, the pitch of a note is determined by the frequency at which it vibrates. Higher frequency vibrations produce higher-pitched notes, while lower frequency vibrations produce lower-pitched notes.
- In human speech, the pitch of a person's voice is determined by the frequency of their vocal cords vibrating. Higher frequency vibrations result in a higher-pitched voice, while lower frequency vibrations result in a lower-pitched voice.

Conclusion
The relationship between frequency and pitch is directly proportional, meaning that as the frequency increases, the pitch also increases. Similarly, as the frequency decreases, the pitch decreases. The frequency of a sound wave also determines its shrillness, with higher frequencies being perceived as more shrill or high-pitched. Therefore, the statement "The frequency determines the shrillness or pitch of a sound" is true.

Sound

Silencing devices should be installed in industrial machines, as well as aircraft engines and transport vehicles, to control the sources of noise and reduce noise pollution effectively.

A larger amplitude of vibration results in a louder sound because it indicates that the sound wave carries more energy.

Sound is a kind of energy:
- Sound is a form of energy that is produced by vibrating objects.
- When an object vibrates, it creates sound waves that travel through the air or other mediums.
- Sound energy is a type of mechanical energy because it involves the movement of particles in the medium through which it travels.
- The energy of sound is transferred from the vibrating source to the surrounding particles, causing them to vibrate as well.
- The energy in sound waves can be measured in units such as decibels (dB).
- Sound energy can be converted into other forms of energy, such as electrical energy in a microphone or mechanical energy in a speaker.
- The intensity or loudness of sound is related to the amount of energy it carries.
- The pitch or frequency of sound is related to the speed at which the vibrations occur.
- Sound waves can be reflected, refracted, absorbed, or transmitted depending on the properties of the medium they encounter.
- Sound energy is essential for communication and allows us to perceive and interpret the world around us through hearing.
In conclusion, sound is a type of energy that is produced by vibrating objects and travels through a medium. It plays a crucial role in our daily lives and is involved in various phenomena and processes.

Understanding Unpleasant Sounds: Noise
When discussing sound, it’s essential to differentiate between pleasant and unpleasant auditory experiences.
Definition of Noise
- Noise is typically defined as any unwanted or disruptive sound that can cause annoyance or discomfort.
- It can vary in frequency and intensity, often leading to stress or disturbance in one’s environment.
Characteristics of Noise
- Unpleasantness: Noise is generally perceived as unpleasant and can create a hostile or irritating atmosphere.
- Variety of Sources: Common sources of noise include traffic, construction, loud music, and machinery.
Contrast with Other Terms
- Melody: Refers to a sequence of musical notes that are perceived as a single entity. Melodies are usually harmonious and pleasant to the ear.
- Echo: Involves the reflection of sound waves off surfaces, creating a repeated sound effect. While echoes can be interesting, they are not inherently unpleasant.
- Rhythm: Pertains to the pattern of sounds in music, often contributing to its appeal. Rhythm can enhance the enjoyment of music rather than detract from it.
Conclusion
In summary, the correct answer to the question regarding unpleasant sounds is option 'B' - Noise. Understanding the concept of noise helps to appreciate the importance of sound management in our daily environments, promoting well-being and comfort.

Explanation:

Loud Sound:
- When sound vibrations have a large amplitude, they create a higher intensity of sound waves.
- This higher intensity results in a louder sound being produced.
- The larger the amplitude of the sound vibrations, the more energy is transferred to the surrounding air molecules, causing them to vibrate more vigorously and creating a louder sound.
Therefore, large amplitude of sound vibrations will produce a loud sound.

Understanding Noise Pollution
Noise pollution refers to the excessive or harmful levels of noise in the environment, which can lead to various health issues and environmental disturbances. It is essential to address this issue for the well-being of individuals and ecosystems.
Why Minimize Noise Pollution?
- Health Effects: Prolonged exposure to high noise levels can cause stress, hearing loss, sleep disturbances, and cardiovascular issues.
- Environmental Impact: Noise pollution disrupts wildlife, affecting communication, mating rituals, and natural habitats.
- Quality of Life: High noise levels can lead to decreased productivity, disturbed peace in communities, and overall lower life satisfaction.
Correct Choice: Minimize
The correct answer is "minimize" because:
- Reduction Approach: The goal is to reduce harmful noise levels rather than increase or ignore them. This entails implementing regulations, promoting quiet technologies, and encouraging community awareness.
- Proactive Measures: Strategies such as sound barriers, zoning laws, and public awareness campaigns can effectively minimize noise pollution.
- Long-term Benefits: Minimizing noise pollution leads to healthier populations, improved wildlife habitats, and enhanced overall quality of life.
Conclusion
In conclusion, minimizing noise pollution is crucial for maintaining health and environmental balance. By actively working to reduce noise levels, societies can foster healthier living conditions and protect natural ecosystems. Thus, the emphasis should always be on minimizing rather than amplifying or ignoring noise pollution.

The number of oscillations or vibrations per second is referred to as the frequency of oscillation. It determines how often the particles of the medium vibrate when a sound wave passes through.

The correct answer is option 'C' - vibration.

Explanation:
Motion refers to the change in position of an object with respect to its surroundings. When an object moves back and forth in a repeating pattern, it is said to exhibit to and fro motion. This type of motion is characterized by the object oscillating or vibrating between two points.

Vibration is defined as the rapid to and fro motion of an object about an equilibrium position. It involves the object moving back and forth repeatedly in a periodic manner. The object undergoes a cycle of motion where it moves away from its equilibrium position, reaches a maximum displacement, and then returns to its original position. This cycle of motion is repeated continuously.

Vibration can occur in various forms and can be observed in different objects and systems. Some common examples of vibration include the swinging of a pendulum, the back-and-forth motion of a spring, the shaking of a guitar string, or the oscillation of a tuning fork.

The motion of vibration can be described by several parameters:

1. Amplitude: The maximum displacement or distance traveled by the object from its equilibrium position during vibration.
2. Frequency: The number of complete cycles or oscillations the object undergoes in a given time period.
3. Period: The time taken for one complete cycle or oscillation.
4. Phase: The position of the vibrating object at a specific point in time during its cycle.

Vibration is a fundamental concept in physics and is closely related to the behavior of waves. Waves can be defined as the transfer of energy through a medium without the transfer of matter. They can be categorized into mechanical waves (requiring a medium for propagation) and electromagnetic waves (not requiring a medium). Vibration is a type of mechanical wave.

In conclusion, the to and fro motion of an object is called vibration. This motion involves the object oscillating or vibrating between two points in a periodic manner. Vibration is characterized by parameters such as amplitude, frequency, period, and phase.

Larynx the another name of voice box

Understanding Dog Hearing Capabilities
Dogs possess remarkable auditory abilities, allowing them to hear sounds at higher frequencies than humans. While humans can typically hear sounds ranging from 20 Hz to 20,000 Hz (20 kHz), dogs can detect frequencies as high as 40,000 Hz (40 kHz) or even more.

Frequency Range of Dogs
- Dogs can hear sounds of frequencies higher than **20,000 Hz**.
- This ability enables them to detect high-pitched noises that are inaudible to the human ear.

Evolutionary Advantage
- The heightened sense of hearing is an evolutionary trait that aids in their survival.
- It helps dogs detect potential dangers, such as the sounds of predators or prey, in their environment.

Applications of Dog Hearing
- This acute hearing is utilized in various fields, such as search and rescue operations, where dogs can locate missing persons by hearing specific sounds.
- Dogs are also employed in roles like detecting medical conditions and in law enforcement for sniffing out drugs and explosives.

Conclusion
In summary, dogs can hear frequencies above **20,000 Hz**, making option 'D' the correct answer. Their extraordinary auditory perception not only enhances their interaction with the world but also underscores their value in various roles alongside humans.

Understanding Sound Propagation in Different Mediums
Sound is a mechanical wave that requires a medium to travel, and its speed and intensity vary significantly across gases, liquids, and solids.
Why Sound Travels Fastest in Solids
- Density and Elasticity: Solids have tightly packed molecules, which allows sound waves to transfer energy more efficiently. The higher density and elasticity of solids mean that when one molecule vibrates, it can quickly transmit that vibration to neighboring molecules.
- Molecular Arrangement: In solids, the close arrangement of particles facilitates faster transmission of sound waves. The particles can transmit vibrations through compressions and rarefactions more effectively than in liquids or gases.
Comparison with Liquids and Gases
- Liquids: Sound travels faster in liquids than in gases due to the closer proximity of molecules compared to gases. However, the lack of the same level of rigidity and density as solids limits its speed.
- Gases: In gases, molecules are far apart, leading to slower sound propagation. The energy transfer is less efficient because the molecules have more freedom to move, which results in decreased interaction.
Conclusion
In summary, sound propagates the fastest in solids due to their structural properties, such as high density and strong intermolecular forces. The efficiency of energy transfer in solids is significantly higher than in liquids and gases, making option 'C' the correct answer for the question regarding sound propagation.

Yes, the pitch of a sound is determined by the frequency of the sound waves. The higher the frequency of the sound waves, the higher the pitch of the sound. Low frequency sound waves have a lower pitch.

An object with a frequency of 20 Hz oscillates 20 times per second, as frequency (Hz) represents the number of oscillations per second.

Understanding Frequency
Frequency refers to the number of occurrences of a repeating event per unit of time. In the context of waves, sound, and light, frequency is a crucial concept that defines how often a wave oscillates in a given time period.
Units of Frequency
- The standard unit of frequency is the Hertz (Hz).
- 1 Hz is defined as one cycle per second.
Why Hertz (Hz)?
- Hertz is a derived unit used in the International System of Units (SI).
- It quantifies how frequently an event (like a wave) occurs in a second, making it the most suitable measurement for periodic phenomena.
Comparison with Other Units
- Joules: A unit of energy, not related to frequency.
- Newtons: A unit of force, also unrelated to how often something occurs.
- Decibels: A unit for measuring the intensity of sound, but not frequency itself.
Applications of Frequency
- Frequency is critical in various fields such as physics, engineering, and telecommunications.
- Understanding frequency helps in the analysis of sound waves, radio waves, and even electrical signals.
Conclusion
In summary, frequency is expressed in Hertz (Hz), making option 'D' the correct answer. It is essential to distinguish frequency from other units like Joules, Newtons, and Decibels, as they pertain to different physical quantities. Understanding this concept is vital for various scientific and technical applications.

Because solid are tightly packed and it can pass through it easy

Answer:-(B) Sound needs a material medium for their propagation like solid, liquid or gas to travel because the molecules of solid, liquid and gases carry sound waves from one point to another.
So it is the false statement.

The eardrum senses the vibrations of sound and converts them into neural signals, which are then interpreted by the brain as sound.

Excessive or unwanted sounds lead to noise pollution, which can have negative effects on human health and well-being, such as stress and hearing loss.

Sound is produced by objects that vibrate. These vibrations create sound waves that travel through a medium to reach our ears.

Explanation:
The statement mentioned is true. Here is a detailed explanation:
1. Sound and Vibrations:
- Sound is a form of energy that is produced when vibrations travel through a medium, such as air, water, or solids.
- Vibrations are the rapid back-and-forth movements of particles or objects, which create waves that transfer energy.
2. Propagation of Vibrations:
- When an object vibrates, it causes neighboring particles or objects to vibrate as well.
- These vibrations are transmitted through the medium in a wave-like manner, resulting in the propagation of sound.
3. How Sound Propagates:
- As the vibrating object moves back and forth, it compresses and rarefies the surrounding particles or molecules in the medium.
- This creates a series of compressions and rarefactions, forming a sound wave.
- The sound wave then travels through the medium, with particles oscillating around their equilibrium positions.
4. Characteristics of Sound:
- Sound waves have several characteristics, including frequency, wavelength, amplitude, and speed.
- The frequency determines the pitch of the sound, while the amplitude determines its loudness.
- The wavelength represents the distance between two consecutive compressions or rarefactions.
5. Perception of Sound:
- When sound waves reach our ears, they cause the eardrums to vibrate.
- These vibrations are then transmitted to the inner ear, where they are converted into electrical signals that are sent to the brain.
- The brain interprets these signals as sound, allowing us to perceive and understand it.
In conclusion, the statement is true as sound is indeed caused by the propagation of vibrations through a medium.