Sound Archives

21. Which one of the following statements is not correct?

Which one of the following statements is not correct?

Pitch of a sound is its characteristic by which we can generally differentiate between a male voice and a female voice.

The loudness of sound is related to its frequency.

A musical sound has certain well-defined frequencies which are generally harmonics of a fundamental frequency.

The timbre of a particular musical sound is related to the waveform of the sound wave.

This question was previously asked in

UPSC NDA-2 – 2016

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The loudness of sound is primarily related to the intensity of the sound wave, which is proportional to the square of its amplitude. Frequency, on the other hand, determines the pitch of the sound. A higher frequency corresponds to a higher pitch, while a larger amplitude corresponds to a louder sound. Therefore, the statement that the loudness of sound is related to its frequency is incorrect.

Loudness relates to amplitude (intensity), while pitch relates to frequency. Timbre relates to waveform (harmonics).

Statement A is correct: Pitch helps differentiate voices; female voices typically have higher fundamental frequencies (and thus higher pitch) than male voices. Statement C is correct: Musical sounds are typically periodic and composed of a fundamental frequency and its harmonic overtones. Statement D is correct: Timbre, or quality, is determined by the combination and relative intensity of overtones present in addition to the fundamental frequency, which shapes the waveform and allows us to distinguish between different instruments or voices.

22. Which one of the following statements is correct?

Which one of the following statements is correct?

The speed of sound waves in a medium depends upon the elastic property of the medium but not on inertia property.

The speed of sound waves in a medium depends upon the inertia property of the medium but not on elastic property.

The speed of sound waves in a medium depends neither on its elastic property nor on its inertia property.

The speed of sound waves in a medium depends both on elastic and inertia properties of the medium.

This question was previously asked in

UPSC NDA-2 – 2016

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The speed of sound waves in a medium is determined by the medium’s properties related to elasticity and inertia. Sound waves are mechanical waves, meaning they propagate through a medium by causing particles of the medium to oscillate. The elastic property (like Bulk modulus or Young’s modulus) determines how easily the medium restores its shape or volume after being deformed by the wave. The inertia property (density) determines how much resistance the medium offers to changes in motion. The speed of sound increases with increasing elasticity and decreases with increasing density. Therefore, the speed of sound depends on both properties.

Speed of mechanical waves depends on the elastic modulus and density of the medium. Higher elasticity allows faster propagation of disturbances. Higher density provides more inertia, resisting quick motion.

The formula for the speed of sound in a fluid is $v = \sqrt{B/\rho}$, where B is the Bulk modulus and $\rho$ is the density. For a solid rod, $v = \sqrt{Y/\rho}$, where Y is Young’s modulus. These formulas explicitly show dependence on both an elastic property and density.

23. When sound waves are propagated through a medium, the physical quantit

When sound waves are propagated through a medium, the physical quantity/ quantities transmitted is/are

matter only

energy only

energy and matter only

energy, momentum and matter

This question was previously asked in

UPSC NDA-2 – 2016

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Sound waves are mechanical waves that transfer energy through a medium by causing particles of the medium to vibrate about their equilibrium positions.

Waves, in general, are mechanisms for transferring energy and momentum without transferring matter over a macroscopic distance. In sound waves, the particles of the medium oscillate but do not travel along with the wave.

While particles have momentary momentum as they oscillate, and momentum is technically transferred by sound waves, the primary and most commonly cited quantity transmitted by sound waves in this context is energy. Option D is incorrect because matter (bulk material) is not transmitted. Given the options, B is the most appropriate answer representing the main quantity transferred.

24. The loudness of sound is related to:

The loudness of sound is related to:

its frequency

its amplitude

its speed

its pitch

This question was previously asked in

UPSC NDA-2 – 2015

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The loudness of a sound is related to its intensity, which in turn is proportional to the square of the amplitude of the sound wave. A sound wave with a larger amplitude carries more energy and is perceived as louder.

Loudness is the perceptual attribute of sound that is most closely related to the intensity of the sound wave, which depends on its amplitude.

Frequency is related to pitch (how high or low a sound is). The speed of sound depends on the medium through which it travels, not its loudness. Pitch is determined by frequency. While frequency and waveform also contribute to the overall perception of sound, amplitude is the primary determinant of loudness. Loudness is typically measured in decibels (dB).

25. Which one of the following does not apply to sound waves in fluids ?

Which one of the following does not apply to sound waves in fluids ?

They transport energy

They need a medium to travel

They are transverse

They travel faster in liquids than in gases

This question was previously asked in

UPSC NDA-1 – 2024

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The statement that does not apply to sound waves in fluids (liquids and gases) is that they are transverse. This corresponds to option C.

Sound waves are mechanical waves that require a medium to propagate. In fluids (liquids and gases), sound waves are longitudinal waves, meaning the particles of the medium vibrate parallel to the direction of wave propagation, creating areas of compression and rarefaction.

Options A, B, and D are true for sound waves. A) They transport energy. B) They need a medium to travel (they cannot travel in a vacuum). D) Sound generally travels faster in denser, less compressible media. Liquids are generally denser and less compressible than gases, leading to higher sound speeds in liquids compared to gases. Transverse waves, where particle motion is perpendicular to wave propagation, can occur for sound in solids (shear waves) but not in fluids.

26. Which one among the following is true for the speed of sound in a give

Which one among the following is true for the speed of sound in a given medium ?

Speed of sound remains same at all frequencies

Speed of sound is faster at higher frequencies

Speed of sound is slower at higher frequencies

Speed of sound is slower at higher wavelengths

This question was previously asked in

UPSC NDA-1 – 2023

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The speed of sound in a given medium is primarily determined by the properties of the medium itself, such as its elasticity (or compressibility) and density. In a specific medium under uniform conditions (like constant temperature and pressure for air), the speed of sound is generally constant and independent of the frequency or wavelength of the sound wave. The relationship v = fλ (speed = frequency × wavelength) holds true, meaning that if the frequency changes, the wavelength changes accordingly to keep the speed constant.

– Speed of sound depends on the properties of the medium (elasticity and density).
– For a given medium under specific conditions, the speed of sound is constant.
– The relationship v = fλ implies an inverse relationship between frequency (f) and wavelength (λ) for a constant speed (v).
– In contrast, for light waves in a *dispersive* medium (like glass), speed *does* depend on frequency/wavelength. However, for sound waves in typical media like air, water, or solids, dispersion effects related to frequency are usually negligible unless considering very specific materials or high frequencies outside the audible range.

Factors that affect the speed of sound in air include temperature (speed increases with temperature), humidity (speed increases slightly with humidity), and pressure (for an ideal gas, speed is independent of pressure at constant temperature and density). The speed of sound is generally fastest in solids, slower in liquids, and slowest in gases.

27. Which one of the following statements is not true for a flute, a mus

Which one of the following statements is not true for a flute, a musical instrument ?

Momentum of waves on the blowing jet determines the loudness of the produced note.

Arrival time of the waves on the blowing jet determines the pitch of the produced note.

Sound comes from a vibrating column of air inside the flute.

Sound comes from a vibrating column of air inside as well as outside the flute.

This question was previously asked in

UPSC NDA-1 – 2023

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In a flute, the sound primarily originates from the vibration of the column of air *inside* the tube. The tube acts as a resonant cavity that reinforces specific frequencies of vibration initiated by the air jet blown across the lip plate.

While there is complex airflow and some turbulence outside the flute, the characteristic musical tone and pitch are produced by the standing waves formed within the air column confined by the tube. The tube length (modified by finger holes) determines the resonant frequencies (pitches).

Statement A is plausible as the force/momentum of the air jet relates to the energy input and amplitude of vibration, affecting loudness. Statement C is true, describing the essential mechanism. Statement B is also arguably true in the sense that the timing of feedback from the air column resonance influences the jet’s oscillation rate, thus affecting the pitch. However, stating that sound comes from a vibrating column of air *outside* as a *main* source is incorrect; the primary resonant vibration is internal.

28. The sound created in a big hall persists because of the repeated refle

The sound created in a big hall persists because of the repeated reflections. The phenomenon is called

Reverberation.

Dispersion.

Refraction.

Diffraction.

This question was previously asked in

UPSC NDA-1 – 2021

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The phenomenon where sound persists in a big hall because of repeated reflections is called A) Reverberation.

– Reflection of sound waves occurs when they bounce off surfaces.
– In an enclosed space, sound waves reflect repeatedly from walls, ceilings, and other surfaces.
– Reverberation is the persistence of sound after the source has stopped, caused by these multiple reflections delaying the sound’s decay.

– Dispersion is the splitting of waves based on wavelength (e.g., light into colours).
– Refraction is the bending of waves as they pass from one medium to another.
– Diffraction is the bending of waves around obstacles or through openings.
– While reflection is the mechanism, the *persistence* of sound due to these multiple reflections is specifically termed reverberation. Excessive reverberation can make sound unclear in large halls.

29. At 20°C, the speed of sound in water is approximately

At 20°C, the speed of sound in water is approximately

330 m/s

800 m/s

1500 m/s

5000 m/s

This question was previously asked in

UPSC NDA-1 – 2019

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The correct answer is (C) 1500 m/s.

The speed of sound varies significantly depending on the medium and its temperature. Sound travels faster in denser media (liquids and solids) compared to gases because particles are closer together, allowing vibrations to be transmitted more quickly.

At 20°C, the speed of sound in air is approximately 343 m/s. In pure water at 20°C, the speed of sound is typically around 1482 m/s. Option (C) 1500 m/s is the closest approximation among the given choices for the speed of sound in water at this temperature. The speed of sound in solids like steel can be much higher, around 5000-6000 m/s.

30. Which one of the following frequency ranges is sensitive to human ears

Which one of the following frequency ranges is sensitive to human ears ?

0 – 200 Hz

20 – 20,000 Hz

200 – 20,000 Hz only

2,000 – 20,000 Hz only

This question was previously asked in

UPSC NDA-1 – 2018

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The correct answer is B) 20 – 20,000 Hz.

The typical range of frequencies that the human ear can perceive is from approximately 20 Hertz (Hz) to 20,000 Hertz (or 20 kilohertz, kHz). Sounds with frequencies below 20 Hz are called infrasound, and those above 20,000 Hz are called ultrasound; neither is audible to humans under normal conditions. While the sensitivity varies significantly with age (higher frequencies are often less audible as people get older), the range 20-20,000 Hz represents the general limits of human hearing.

The human ear is most sensitive to frequencies between 1,000 Hz and 4,000 Hz. The ability to hear high frequencies tends to decrease with age, a phenomenon known as presbycusis. Other animals have different hearing ranges; for example, dogs can hear much higher frequencies than humans (up to 45,000-65,000 Hz).