Name: why sound moves faster in dense materials
Uploaded: 2023-04-30T11:11:05.000Z
Duration: 51 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 Solids and Liquids

מוצקים ונוזלים אינם ניתנים לדחיסה בקלות. כאשר גלי קול מחליפים את החלקיקים המרכיבים אותם במדיות אלה, הם מפגינים נטייה לחזור למיקומם המקורי עקב כוחות בין-חלקיקיים.
נזכיר כי קול הוא גל לחץ. הוא נע בתווך כאשר מרכיביו רוטטים לגבי מיקומם הממוצע ומעבירים את האנרגיה לחלקיקים שכנים.
אם החלקיקים המרכיבים אותם הם מאסיביים, קשה יותר לשחזר אותם למיקומם המקורי. לפיכך, מהירות הקול דרך מדיום נמוכה יותר אם מרכיביו כבדים יותר.
בשילוב מושגים אלה, מהירות הקול במוצקים ובנוזלים ניתנת על ידי השורש הריבועי של המודולוס האלסטי חלקי צפיפות התווך המתאים.

מהירות הקול במוצקים ובנוזלים

<div style="direction:rtl">

 רוב המוצקים והנוזלים אינם ניתנים לדחיסה—הצפיפות שלהם נשארת קבועה לאורך כל הדרך. בנוכחות כוח חיצוני, המולקולות נוטות לחזור למקומן המקורי, מה שמתאפשר רק בגלל אינטראקציה בין המרכיבים. האינטראקציות עוזרות למרכיבים להעביר מידע על הפרעות חיצוניות, כמו גלי קול. לכן, גלי קול נעים מהר יותר דרך המדיה הללו. בהשוואה למוצקים, המרכיבים בנוזל קשורים פחות בחוזקה. לפיכך, גלי קול איטיים יותר בנוזלים מאשר במוצקים. יתר על כן, במוצקים, גלי הקול אינם אורכיים בלבד; הם גם נוסעים בכיוון הרוחבי. 

 ניתן לגזור את מהירות הקול במוצקים ובנוזלים על ידי יישום חוקי התנועה של ניוטון על עמודה של מדיום ההתפשטות. בדרך כלל, מהירות הקול במוצק או בנוזל היא השורש הריבועי של היחס בין הכוח המחזיר את החלקיקים למצב שיווי המשקל שלהם, לבין האינרציה המתנגדת לשחזור. ניתן להבין את השורש הריבועי אם נזכור שמונח המהירות מופיע כריבוע במשוואת הגלים הליניארית. מודול יאנג קובע את כוח השיקום במוצקים, וצפיפותו קובעת את האינרציה. לפיכך, מהירות הקול במוצק היא השורש הריבועי של מודול ה-Young שלו חלקי הצפיפות. באופן דומה, בנוזלים, מהירות הקול נתונה על ידי השורש הריבועי של מודול ה- Bulk שלו חלקי הצפיפות שלו. 

 טקסט זה מותאם מ <a href="https://openstax.org/books/university-physics-volume-1/pages/17-2-speed -of-sound">Openstax, University Physics Volume 1, Section 17.2: Speed of Sound.</a>

 </div>

רוב המוצקים והנוזלים אינם ניתנים לדחיסה – צפיפותם נשארת קבועה לאורך כל הדרך. בנוכחות כוח חיצוני, המולקולות נוטות ...

Education

JoVE Core

פיזיקה

Unit 1

יחידה 1

Sound

צליל

KEY TERMS AND CONCEPTS

מונחים ומושגים מרכזיים

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 travels faster in these media than it does in gases. Sound is usually slower in liquids than in solids because the particles in a liquid are not as tightly bound. In solids, sound waves are also not purely longitudinal. They can move in the lateral direction as well.

The speed of sound in a solid or liquid can be derived by applying Newton’s laws of motion to a column of the medium. In general, the speed depends on the balance between restoring force and inertia. The restoring force is what pulls particles back to equilibrium. Inertia is the resistance to that motion.

For solids, the restoring force is set by Young’s modulus, and the inertia is set by density. That is why the speed of sound in a solid equals the square root of Young’s modulus divided by density. In liquids, the matching quantity is the bulk modulus. So the speed of sound in a liquid equals the square root of bulk modulus divided by density.

Because density changes with temperature, the speed of sound in any solid or liquid also changes with temperature. The square root form of the formulas reflects the wave equation, where speed appears as a squared term. This relationship helps explain why material properties control how sound travels through matter.

Why Sound Moves Faster in Dense Materials

why-sound-moves-faster-in-dense-materials

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...

/files/media/science-education/science-education-thumbs/14724.jpg

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

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

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...

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...

/files/media/science-education/science-education-thumbs/14725.jpg

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...

/files/media/science-education/science-education-thumbs/14726.jpg

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...

/files/media/science-education/science-education-thumbs/14727.jpg

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...

/files/media/science-education/science-education-thumbs/14728.jpg

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...

/files/media/science-education/science-education-thumbs/14729.jpg

key terms and concepts

Learn why sound travels faster in solids and liquids, how Young’s modulus and bulk modulus affect speed, and why density and temperature matter.

Why Sound Moves Faster in Dense Materials | 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

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.

Speed of Sound Waves in Different Media

Travelling Waves

A wave is a disturbance that propagates from its source, repeating itself periodically, and is typically associated with simple harmonic motion. ...

Wave Parameters

The simplest mechanical waves are associated with simple harmonic motion and repeat themselves for several cycles. These simple harmonic waves can be ...

Equations of Wave Motion

Mathematically, the motion of a wave can be studied using a wavefunction. Consider a string oscillating up and down in simple harmonic motion, having a ...

Graphing the Wave Function

Consider the wave equation for a sinusoidal wave moving in the positive x-direction. The wave equation is a function of both position and time. From the ...

/files/media/science-education/science-education-thumbs/14721.jpg

Velocity and Acceleration of a Wave

A wave propagates through a medium with a constant speed, known as a wave velocity. It is different from the speed of the particles of the medium, which ...

Speed of a Transverse Wave

The speed of a wave depends on the characteristics of the medium. For example, in the case of a guitar, the strings vibrate to produce the sound. The ...

/files/media/science-education/science-education-thumbs/14722.jpg

problem-solving-tuning-of-a-guitar-string

Problem-Solving: Tuning of a Guitar String

In the case of stringed instruments like the guitar, the elastic property that determines the speed of the sound produced is its linear mass density or ...

/files/media/science-education/science-education-thumbs/14744.jpg

Kinetic and Potential Energy of a Wave

All forms of waves carry energy; this is directly visualized in nature. For instance, the waves of earthquakes are so intense that they can shake huge ...

Energy and Power of a Wave

The total energy associated with a wavelength is the sum of the potential energy and the kinetic energy. The average rate of energy transfer associated ...

Sound Waves

Sound waves can be thought of as fluctuations in the pressure of a medium through which they propagate. Since the pressure also makes the medium&#39;s ...

Sound as Pressure Waves

Sound waves, which are longitudinal waves, can be modeled as the displacement amplitude varying as a function of the spatial and temporal coordinates. As ...

Perception of Sound Waves

The human ear is not equally sensitive to all frequencies in the audible range. It may perceive sound waves with the same pressure but different ...

Most solids and liquids are incompressible&#8212;their densities remain constant throughout. In the presence of an external force, the molecules tend to ...

Speed of Sound in Gases

The speed of sound in a gaseous medium depends on various factors. Since gases constitute molecules that are free to move, they are highly compressible. ...

Electromagnetic Waves

James Clerk Maxwell formulated a single theory combining all the electric and magnetic effects scientists knew during that time, calling the phenomena his ...

Electromagnetic Wave Equation

Maxwell&#39;s equations for electromagnetic fields are related to source charges, either static or moving. These fields act on a test charge, whose ...

Plane Electromagnetic Waves I

The existence of combined electric and magnetic fields that propagate through space as electromagnetic (EM) waves is the most significant prediction of ...

Electromagnetic Waves in Matter

Electromagnetic waves can travel in the vacuum as well as in matter. For example light, which is an electromagnetic wave, can travel through air, water, ...

Energy Carried By Electromagnetic Waves

Anyone who has used a microwave oven knows there is energy in electromagnetic waves. Sometimes, this energy is obvious, such as in the summer sun&#39;s ...

Intensity Of Electromagnetic Waves

The energy transport per unit area per unit time, or the Poynting vector, gives the energy flux of an electromagnetic wave at any specific time. For a ...

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.

Why Sound Moves Faster in Dense Materials

Description

Transcript

More videos by Standards