Name: what changes sound speed in gases?
Uploaded: 2023-04-30T11:11:13.000Z
Duration: 1 min 8 s
Channel: JoVE

K12 Standards

north-carolina-k-12-science-standard-course-of-study

NC K-12 Science Standard Course of Study

9-12

Physics

waves-and-their-applications-in-technologies-for-information-transfer

Waves and Their Applications in Technologies for Information Transfer

PS.Phy.7.1

Speed of Sound in Gases

음파가 가스 기둥을 통과할 때 파동과 기체 성분 사이에 열이 교환되지 않습니다.
유체 역학의 연속성 방정식, 뉴턴의 운동 제 2 법칙, 밀도 정의 및 열역학 방정식을 사용하여 가스의 음속을 추론 할 수 있습니다. 그것은 가스의 구성과 온도에 달려 있습니다.
모든 가스를 통한 음속은 양과 관련된 방정식에서 알려진 특성을 대체하여 수치로 추정할 수 있습니다.
0°C의 온도에서 공기 중의 음속은 초당 331미터입니다. 같은 온도에서 이산화탄소는 초당 259m, 수소 가스는 초당 1254m입니다.
공기 중의 음속은 전파되는 음파의 주파수와 무관합니다. 따라서 서로 다른 음높이로 악기를 연주하는 음악가 밴드가 완벽하게 동기화된 것처럼 보입니다.

가스에서의 소리의 속도

기체 매질에서 소리의 속도는 다양한 요인에 따라 달라집니다. 가스는 자유롭게 움직이는 분자를 구성하기 때문에 압축성이 높습니다. 따라서 음파는 가스를 통해 천천히 이동합니다. 열역학은 가스의 압력, 부피 및 온도 사이의 관계를 이해하는 데 도움이 되므로 이상 가스의 소리 속도는 열역학 법칙을 사용하여 결정할 수 있습니다. 동시에 뉴턴의 운동 법칙과 유체 역학의 연속 방정식도 유용합니다.

기체 내에서 소리의 속도는 보편적인 기체 상수와 특정 기체의 특성에 따라 달라집니다. 소리의 속도는 기체 성분에 따라 달라집니다. 가스의 온도에 따라서도 변합니다. 그러나 속도는 온도의 제곱근에 따라 변하기 때문에 이러한 변화는 급격하지 않습니다. 예를 들어, 20°C의 공기 중 소리 속도는 0°C의 공기 중 소리 속도보다 4% 더 빠릅니다.

공기 중 소리의 속도는 소리의 주파수에 의존하지 않습니다. 만약 그렇다면 소리에 대한 우리의 인식은 달라졌을 것입니다. 친숙한 소리 소스는 서로 다른 주파수의 소리가 선형으로 중첩되어 있기 때문입니다.

이 텍스트는 <a .="" href="https://openstax.org/books/university-physics-volume-1/pages/17-2-speed-of-sound">Openstax, 대학 물리학 1권, 섹션 17.2: 음속.</a>

기체 매체에서 음속은 다양한 요인에 따라 달라집니다. 기체는 자유롭게 움직일 수 있는 분자로 구성되어 있기 때문에 압축성이 높습니다. ...

Education

교육

JoVE Core

물리학

Unit 1

제1단원

Sound

소리

KEY TERMS AND CONCEPTS

주요 용어 및 개념

what changes sound speed in gases?

Sound speed in gases depends on gas properties, pressure, volume, and temperature. Gas molecules move freely, so gases are highly compressible. Because of that compressibility, sound waves travel more slowly through gases than through many other media.

The speed of sound in an ideal gas can be found using thermodynamics. Thermodynamics links pressure, volume, and temperature, which helps describe how sound moves through a gas. Newton's laws of motion and the continuity equation from fluid dynamics also help explain this motion.

The speed of sound also depends on the gas itself. It changes with the gaseous constituents and with the universal gas constant. Temperature matters too, but the change is not large because the speed varies with the square root of temperature. For example, sound travels only about 4% faster in air at 20 °C than in air at 0 °C.

Sound speed in air does not depend on frequency. If frequency changed the speed, our perception of sound would be different. That is because familiar sounds are built from a linear superposition of many frequencies.

What Changes Sound Speed in Gases?

sound waves

How Sound Travels Through Matter

Sound travels through matter as pressure changes in a medium. These changes make the particles of the medium move back and forth around their mean position. Sound can also be modeled as particle displacement as the wave passes through air, water, or another material. In most fluids, sound waves are longitudinal waves. That means the particles vibrate in the same direction that the wave moves. Fluids do not support lateral pressure well, so sound in liquids and gases mainly moves this way. <br...

sound as pressure waves

Sound Pressure in Longitudinal Waves

Sound waves are longitudinal waves that create changing pressure in a medium. Their displacement amplitude can be modeled as a function of position and time. As one column of the medium moves, nearby columns also move. The difference between these successive displacements produces a pressure change compared with the surrounding pressure. This pressure change is called gauge pressure. It varies across the medium because the pressure fluctuation depends on how much one point is displaced...

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perception of sound waves

How Ear Sensitivity Shapes Sound

The human ear does not respond the same way to every sound frequency. Sounds with the same pressure can seem louder or softer when their frequencies change. Ear health also affects this perception, and hearing can decline with age. Regular exposure to loud noises may also damage the ears over time. Pitch depends on both frequency and pressure amplitude, which is the size of the sound wave’s pressure change. Two sounds with the same frequency and pressure amplitude have the same pitch. If the...

speed of sound in solids and liquids

Why Sound Moves Faster in Dense Materials

Sound moves faster in solids and liquids because their particles are close together and can pass along disturbances quickly. Most solids and liquids are incompressible, which means their densities stay nearly constant throughout. When an external force acts on them, the molecules try to return to their original positions. That restoring motion happens because the particles interact with one another. These interactions let sound waves carry information through the material. As a result, sound...

speed of sound in gases

Sound speed in gases depends on gas properties, pressure, volume, and temperature. Gas molecules move freely, so gases are highly compressible. Because of that compressibility, sound waves travel more slowly through gases than through many other media. The speed of sound in an ideal gas can be found using thermodynamics. Thermodynamics links pressure, volume, and temperature, which helps describe how sound moves through a gas. Newton's laws of motion and the continuity equation from fluid...

deriving the speed of sound in a liquid

Sound Speed in Fluids: Bulk Modulus

Sound speed in fluids depends on a fluid’s bulk modulus and density. These two properties describe how stiff the fluid is and how much inertia it has. For mechanical waves in a fluid, that relationship follows the same pattern used for Young’s modulus and density in solids. The speed of sound in a liquid can be derived by treating the wave as a longitudinal wave moving through the medium. The derivation uses the gauge pressure expression and the impulse-momentum theorem. This same result...

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sound intensity

Measuring How Loud Sound Is

Sound intensity helps describe how loud a sound source is. It depends on how energetically the source vibrates, because those vibrations make the molecules in the medium vibrate as well. Intensity is the energy emitted per unit time per unit area. The area must be perpendicular to the direction the sound wave travels. Using time and area makes the measure reflect the source’s own loudness, even when the source vibrates over a longer time or spreads energy over a larger area. A sound source...

sound intensity level

Measuring Sound with Decibels

Sound intensity level helps measure how loud sound is. The human ear sends sound waves to the brain, and the brain turns those waves into hearing. The loudness of the surrounding environment affects whether a person can tell different sound sources apart. The ear can detect a very wide range of sound intensity. Because of that range, scientists use a logarithmic scale to describe intensity level. Intensity level is a ratio of two intensities, so it has no unit. The standard reference is the...

intensity and pressure of sound waves

Sound Intensity from Displacement and Pressure

Sound intensity can be linked to displacement and pressure in a wave. The key idea is to use the wave expressions and the definition of intensity. To do that, the power carried by the particles is written as force times velocity, and the force per unit area is treated as pressure. The particle velocity can be found from the displacement of the medium. A sinusoidal term averages to zero over time because it is positive and negative for equal parts of each cycle. Its square does not average to...

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sound waves: interference

Sound Wave Interference in Speakers

Sound wave interference can change the loudness of sound when two waves meet. Sound waves may be modeled as longitudinal waves, where molecules move around an equilibrium position, or as pressure waves. When two identical waves from the same source overlap, their crests or troughs can add together. This is called constructive interference, and it increases amplitude. If identical waves start in phase but travel different path lengths, they can become out of phase. Then a crest can meet a...

interference: path lengths

Interference from Different Path Lengths

Interference from different path lengths explains how two sound sources can create changing patterns in space. The sources may or may not start in phase, but they emit waves at the same frequency. When they are in phase, they are called coherent sources, and that is easy to arrange by feeding both speakers from the same source, such as a tuning fork. These synchronized sources start with the same frequency and the same phase. As the waves move outward, they travel different distances to reach...

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sound waves: resonance

Sound Waves in Tubes and Strings

Sound waves can form resonance patterns in strings and tubes when the boundary conditions match the wave frequency. On a string under tension, symmetrical boundary conditions create a node at each end. A node is a fixed point where the string does not move. Some frequencies then produce standing waves, while other frequencies interfere destructively. Resonance also appears in a hollow tube. In a tube closed at one end and open at the other, a vibrating tuning fork near the open end sends an...

beats

Sound Interference and Beats

Sound interference creates beats when two or more close frequencies combine. In music, this shows up as a changing loudness that rises and falls. The pattern comes from superposition, the adding together of waves. Constructive interference makes the sound stronger, while destructive interference makes it weaker. Music usually contains many changing frequencies from instruments and voices. A single sound at one frequency for a long time can feel dull or even irritating. It can sound like the...

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doppler effect - i

Doppler Shift in Sound and Light

The Doppler effect describes how the frequency of a wave changes when the source and the observer move relative to each other. It was named after the Austrian physicist and mathematician Christian Johann Doppler in 1842. He studied both moving sources and moving observers. A simple example is an ambulance passing a person standing on a street corner. As the ambulance approaches, the siren seems louder. As it moves away, the sound gets quieter. The pitch also changes. The high siren sound...

doppler effect - ii

Doppler Radar and Heart Blood Flow

Doppler effect applications appear in weather forecasting and medical imaging. In these uses, a change in frequency helps show motion. The reflected signal can reveal whether an object is moving toward or away from the source. Meteorologists use Doppler radar to study weather events. A transmitter sends radio waves at a set frequency toward the sky from a weather station. The waves bounce off clouds and precipitation and return to the station. If the reflected radio frequency decreases, the...

shock waves

Sonic Booms and Supersonic Motion

Sonic booms and supersonic motion happen when a sound source moves as fast as, or faster than, sound in the medium. In the Doppler formula for sound, it is usually assumed that sound travels faster than the source. When that assumption fails, a shock wave can form. As the source gets close to the speed of sound, successive wavefronts build up by constructive interference right behind it. Scientists once thought this pressure buildup would keep an airplane from breaking the sound barrier and...

echo

Echo Sound and Distance Detection

Echo is a reflected sound that returns after the original sound has been heard. The human ear cannot tell two sounds apart if they arrive within about 0.1 seconds of each other. When the reflected sound takes longer than that to return, the ear hears two separate sounds instead of one. This effect is easy to notice when the sound source is close to a surface that sends the sound back. If the sound and its reflection are separated by enough time, the result is an echo. A minimum distance of...

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key terms and concepts

Explore how gas properties, temperature, and thermodynamics affect the speed of sound in gases, and why frequency does not change sound speed in air.

What Changes Sound Speed in Gases? | JoVE K12

physics

JoVE Core Physics introduces the theory and application of fundamental physics topics, including kinematics, dynamics, fluid mechanics, statics, waves, and acoustics, with concise and easy-to-understand animated videos. Additionally, the scientist-in-action videos demonstrate the application of related concepts in classical and original research experiments performed in today's laboratories worldwide.

Tennessee Academic Standards

High School

PHYS.PS4.2

Virginia  Standards of Learning

HIgh School

Physical Science

PS.6

PS.6.b

new-jersey-student-learning-standards-for-science

New Jersey Student Learning Standards for Science

HS-PS4-2

Arizona Science Standards

HS.P4

HS.P4U1.10

Alabama Course of Study Science

9-12.PS.2.2.c

9-12.P.3.7.b

Next Generation Science Standards

HS-PS4-1

Texas Essential Knowledge and Skills

PHYS.8

PHYS.8.B

new-york-state-science-learning-standards

New York State Science Learning Standards

HS. Waves and Electromagnetic Radiation

HS-PS4-1.

Georgia Standards of Excellence

SPS9.

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Obtain, evaluate, and communicate information to compare mechanical and electromagnetic waves (specifically light and sound) in terms of wave characteristics (frequency, wavelength, period, amplitude, velocity, and energy).

Analyze the behavior of waves and their applications.

What Changes Sound Speed in Gases?

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