Name: sound interference and beats
Uploaded: 2023-05-16T08:18:41.000Z
Duration: 1 min 9 s
Channel: JoVE

K12 Standards

Tennessee Academic Standards

High School

Physics

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

Waves and Their Applications in Technologies for Information Transfer

PHYS.PS4.4

Beats

When two sound waves of equal amplitude and slightly different frequencies interfere with each other, the displacement equation for the resultant wave at a particular position can be determined. Its intensity rises and falls alternately with time.
The total length of the time axis represents one second. When the two waves are in phase, their amplitudes add.
And, when the two waves are exactly out of phase, the total amplitude is zero.
This periodic variation in sound intensity with time forms beats.
The resultant wave looks like a single sinusoidal wave with varying amplitude, which goes through two maxima and two minima in one second. The frequency of this amplitude variation is two hertz.
The number of beats heard per second is called beat frequency and is equal to the difference in frequency of the sound waves.
The time interval between two successive beats is defined as the beat period, which is the inverse of the beat frequency.

klopt

De studie van muziek biedt veel voorbeelden van de superpositie van golven en de constructieve en destructieve interferentie die optreedt. Zeer weinig voorbeelden van muziek die wordt uitgevoerd, bestaan uit een enkele bron die gedurende langere tijd een enkele frequentie afspeelt. Een enkele geluidsfrequentie gedurende een langere periode kan eentonig zijn tot op het punt van irritatie, vergelijkbaar met het ongewenste gedreun van een vliegtuigmotor of een luide ventilator. Muziek is aangenaam en spannend door het mixen van de wisselende frequenties van verschillende instrumenten en stemmen. Een interessant fenomeen dat optreedt als gevolg van de constructieve en destructieve interferentie van twee of meer geluidsfrequenties is het fenomeen beats. Ze zien eruit als een enkele sinusoïdale golf met een variërende amplitude die gaat van maximaal naar nul en terug. De amplitudevariatie veroorzaakt variaties in luidheid, de zogenaamde beats, en de frequentie waarmee de luidheid varieert, wordt de beatfrequentie genoemd. Het wordt gedefinieerd als het verschil tussen de twee frequenties. Pianostemmers kunnen deze beats gebruiken om een piano te stemmen. Er wordt op een stemvork geslagen en er wordt een noot op de piano gespeeld. Wanneer de pianostemmer de snaar stemt, hebben de tellen een lagere frequentie naarmate de frequentie van de gespeelde noot de frequentie van de stemvork nadert. Beslagen tussen twee tonen zijn hoorbaar tot een zwevingsfrequentie van ongeveer 6 of 7 Hz. De motoren van meermotorige propellervliegtuigen moeten worden gesynchroniseerd, zodat de propellergeluiden geen vervelende beats veroorzaken, die te horen zijn als luide kloppende geluiden. Op sommige vliegtuigen gebeurt dit elektronisch; bij andere doet de piloot het op het gehoor, net zoals het stemmen van een piano.

Klopt

The study of music provides many examples of the superposition of waves and the constructive and destructive interference that occurs. Very few examples ...

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

Education

JoVE Core

Natuurkunde

Unit 1

Onderdeel 1

Sound

Geluid

KEY TERMS AND CONCEPTS

BELANGRIJKE TERMEN EN CONCEPTEN

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 steady drone of an aircraft engine or a loud fan. Beats help explain why mixed sounds can be more interesting than one constant tone.

A beat looks like one sinusoidal wave with an amplitude that changes over time. The amplitude goes from a maximum to zero and back again. That changing amplitude causes changes in loudness, which are called beats. The beat frequency is the rate of that loudness change, and it equals the difference between the two frequencies.

Piano tuners use beats to tune a piano. They strike a tuning fork and play the matching note on the piano. As the string is tuned closer to the tuning fork, the beats become slower. Beats between two tones can be heard up to about 6 or 7 Hz.

Beats also matter in multi-engine propeller aircraft. The engines must be synchronized so the propeller sounds do not create annoying beats. If they are not matched, the result can be a loud throbbing sound. On some planes, this is done electronically. On others, the pilot does it by ear, just like tuning a piano.

Sound Interference and Beats

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

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

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 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...

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 how sound waves create beats through interference, why loudness changes, and how piano tuners and pilots use beat frequency in real life.

Sound Interference and Beats | 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.

Virginia  Standards of Learning

HIgh School

Physical Science

PS.6

PS.6.c

PH.5

PH.5.b

Alabama Course of Study Science

9-12

9-12.P.3.7.b

Next Generation Science Standards

HS-PS4-3

south-carolina-college-and-career-ready-science-standards

South Carolina College and Career Ready Science Standards

P-PS4-2

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 ...

Interference and Superposition of Waves

When two waves of the same nature occur in the same region simultaneously, they result in interference. Interference of waves implies that the net effect ...

Know wave parameters (i.e. velocity, period, amplitude, frequency, angular frequency) as well as how these quantities are defined in the cases of longitudinal and transverse waves.    Know wave parameters (i.e. velocity, period, amplitude, frequency, angular frequency) as well as how these quantities are defined in the cases of longitudinal and transverse waves.  EXPLANATION: Standard 4.PS4.1 is a student’s introduction to waves. At this time, students address the properties of amplitude, wavelength and direction of a wave and principles of superposition of waves, but not by name. In 8.PS4.1, students revisit the topic adding frequency to their models and beginning to consider wave speed, but without mentioning factors affecting the speed of the waves. PHYS.PS2.3 includes discussion of rotational motion which can pair with discussions of simple harmonic motion to clarify angular velocity and angular speed. Discussions regarding the origin of waves can fully develop these ideas.

PHYS.PS4.1

Speed of Sound in Solids and Liquids

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. ...

Deriving the Speed of Sound in a Liquid

As with waves on a string, the speed of sound or a mechanical wave in a fluid depends on the fluid&#39;s elastic modulus and inertia. The two relevant ...

propagation-speed-of-electromagnetic-waves

Propagation Speed of Electromagnetic Waves

Electromagnetic waves are consistent with Ampere&#39;s law. Assuming there is no conduction current Ampere&#39;s law is given as:


Consider a plane ...

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, ...

Simple Harmonic Motion

Simple harmonic motion is the name given to oscillatory motion for a system where the net force can be described by Hooke&#39;s law. If the net force can ...

/files/media/science-education/science-education-thumbs/12762.jpg

characteristics-of-simple-harmonic-motion

Characteristics of Simple Harmonic Motion

The key characteristic of the simple harmonic motion is that the acceleration of the system and, therefore, the net force are proportional to the ...

/files/media/science-education/science-education-thumbs/12763.jpg

oscillations-about-an-equilibrium-position

Oscillations about an Equilibrium Position

Stability is an important concept in oscillation. If an equilibrium point is stable, a slight disturbance of an object that is initially at the stable ...

Energy in Simple Harmonic Motion

To determine the energy of a simple harmonic oscillator, consider all the forms of energy it can have during its simple harmonic motion. According to ...

/files/media/science-education/science-education-thumbs/12765.jpg

Frequency of Spring-Mass System

One interesting characteristic of the simple harmonic motion (SHM) of an object attached to a spring is that the angular frequency, and the period and ...

/files/media/science-education/science-education-thumbs/14718.jpg

Describe parameters of a medium that affect the propagation of a sound wave through it. Describe parameters of a medium that affect the propagation of a sound wave through it. EXPLANATION: The focus of this discussion should be properties of the medium, specifically the density of the material. The density becomes a factor in optics and considering transmission of electromagnetic waves. Students can be led to make their descriptions by experimenting with coiled springs stretched to varying lengths. The topic of linear mass density can be used to explore analogous properties in the air.

PHYS.PS4.2

Reflection of Waves

When a wave travels from one medium to another, it gets reflected at the boundary of the second medium. A common example of this is when a person yells at ...

Propagation of Waves

When a wave propagates from one medium to another, part of it may get reflected in the first medium, and part of it may get transmitted to the second ...

Standing Waves

Sometimes waves do not seem to move; rather, they just vibrate in place. Unmoving waves can be seen on the surface of a glass of milk kept in a ...

/files/media/science-education/science-education-thumbs/12783.jpg

Modes of Standing Waves - I

A close look at earthquakes provides evidence for the conditions appropriate for resonance, standing waves, and constructive and destructive interference. ...

/files/media/science-education/science-education-thumbs/12784.jpg

Modes of Standing Waves: II

The starting point for expressing the modes of standing waves is understanding the boundary conditions that the waves must follow. The boundary conditions ...

/files/media/science-education/science-education-thumbs/14723.jpg

Understand that the reflection, refraction, and transmission of waves at an interference between two media can be modeled on the basis of the characteristics of specific wave parameters and parameters of the medium.  Understand that the reflection, refraction, and transmission of waves at an interference between two media can be modeled on the basis of the characteristics of specific wave parameters and parameters of the medium. EXPLANATION: The focus of this standard is on developing an understanding for the behavior of waves at a boundary. To demonstrate these principles, it is suggested that students create waves on a coiled spring or string and send these waves towards either a free or fixed end or through a different weight of string. For instance, wave can be created in a section of a lighter string then transmitted towards a point where that string terminates into a heavier segment of string. In doing so, it is possible to observe the effects on wave amplitude and a discussion of energy differences. Students should extend their observations of these mechanical waves to wave behaviors at other scales.

PHYS.PS4.3

Sound Waves: Interference

Sound waves can be modeled either as longitudinal waves, wherein the molecules of the medium oscillate around an equilibrium position, or as pressure ...

Interference: Path Lengths

Consider two sources of sound, that may or may not be in phase, emitting waves at a single frequency, and consider the frequencies to be the same.
Two ...

Sound Waves: Resonance

Resonance is produced depending on the boundary conditions imposed on a wave. Resonance can be produced in a string under tension with symmetrical ...

Communicate scientific and technical information about how the principle of superposition explains the resonance and harmonic phenomena in air columns on strings and common sound devices. Communicate scientific and technical information about how the principle of superposition explains the resonance and harmonic phenomena in air columns on strings and common sound devices. EXPLANATION:  In 4.PS4.1, students examine the effects of superposition of waves, but do not explore the behavior of waves at boundaries. Building on 4.PS4.3, the behavior of a wave at a free or fixed boundaries can create patterns where successive waves produced by a source interact with those reflected off a boundary. Discussions should include general development of the idea of harmonics. Once established, this topic can be extended to the specific function of stringed instruments such as guitars of simple open or closed tubes. The phenomena of resonance can be produced using a tuning fork held above a section of rigid tubing which is lowered or lifted into a pail of water. Resonance can be heard clearly at multiple points, providing an opportunity to model the source of resonance and relate the resonance points to the wavelength of the wave produced. The phenomenon of beats can be used to provide an introduction to this topic as it too is an audible phenomenon. Quick demonstrations of beats can be performed without tuning forks using multiple open windows in a browser simultaneously playing different frequencies.

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 ...

Generating Electromagnetic Radiations

The German physicist Heinrich Hertz (1857&#8211;1894) was the first to generate and detect certain types of electromagnetic waves in the laboratory. ...

The Electromagnetic Spectrum

Electromagnetic waves are categorized according to their wavelengths and frequencies, giving the electromagnetic spectrum. These waves are classified as ...

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 ...

Anatomy of the Eyeball

The eyeball is a hollow fluid-filled structure composed of three layers&#8212;the fibrous, vascular, and inner layers.
The superficial fibrous layer has ...

Accessory Structures of the Eye

The accessory structures of the eyes protect and support the eye but are not directly involved in vision.&#160;&#160;&#160;&#160;&#160;&#160;
Eyebrows, ...

Focusing of Light in the Eye

In a normal human eye, as light rays enter, they bend at the cornea, and the lens, to form an inverted image on the retina. The extent to which rays ...

Evaluate the characteristics of the electromagnetic spectrum by communicating the similarities and differences among the different bands. Research and determine methods and devices used to measure these characteristics. Evaluate the characteristics of the electromagnetic spectrum by communicating the similarities and differences among the different bands. Research and determine methods and devices used to measure these characteristics. EXPLANATION: The visible portion of the electromagnetic spectrum will be familiar to students, as will the ideas of x-rays, microwaves, and radiowaves. However, students often struggle to see these phenomena as multiple manifestations of the same principles. It may be beneficial to relate these discussions to the physiology of the human eye, specifically the function of the rhodopsin photopigment. As a demonstration: the light bulbs on the front of remote controls emit light outside of the visible spectrum; however, inexpensive cell phone cameras lack IR filters (as well as some front facing cameras on more current cell phones). Rendering the IR light visible can help student to understand that many devices function by capturing the energy of electromagnetic waves. An additional option would be the creation of a crystal radio using a germanium diode.

PHYS.PS4.5

Light as Energy

The energy required to carry out photosynthesis is light&#8212; typically electromagnetic radiation from the sun. The range of all possible wavelengths is ...

dual-nature-of-electromagnetic-em-radiation

Dual Nature of Electromagnetic (EM) Radiation

Electromagnetic (EM) radiation consists of electric and magnetic field components oscillating in planes perpendicular to each other and mutually ...

interaction-of-em-radiation-with-matter-spectroscopy

Interaction of EM Radiation with Matter: Spectroscopy

Electromagnetic (EM) radiation can be considered an oscillating electric and magnetic field propagating through a medium that can interact with matter in ...

Plan and conduct controlled scientific investigations to construct explanations of light’s behavior (reflection, refraction, transmission, interference) including the use of ray diagrams. Plan and conduct controlled scientific investigations to construct explanations of light’s behavior (reflection, refraction, transmission, interference) including the use of ray diagrams. EXPLANATION:  In PHYS.PS4.3 students examine the behaviors of mechanical waves moving through a medium. Though the terminology in this standard is comparable, this standard focuses on optics of light. Students should work with lenses and mirrors to build an understanding of the behaviors of light as it interacts with surfaces (reflection, refraction, transmission). In 4.PS4.1 and PHYS.PS4.1, students investigated interference patterns with mechanical waves. Using a pair of speakers and an online tone/frequency generator, it is possible to demonstrate that sound waves, like mechanical waves, can interfere with each other. In such a demonstration, students are able to hear variations in the volume of the sound as they walk in a straight line across the field of sound created by the speakers.

PHYS.PS4.6

Sound Interference and Beats

Description

Transcript

Tags

More videos by Standards