G11S Phy Ch3,4 Reception of sound Vid 2 of 3 En 20 21

Summary

This educational video explores the reception of sound, contrasting it with the emission of sound from the first part. It explains the working of a loudspeaker, an electro-acoustic converter, and a microphone, an acousto-electric converter. The video also delves into the anatomy of the human ear, detailing how it converts sound vibrations into electrical signals. It discusses the audible frequency range of the human ear, from 20 Hz to 20 kHz, and touches on the applications of ultrasounds, such as in sonar technology for depth measurement and medical imaging.

Takeaways

• 🔊 Sound is a longitudinal mechanical wave generated by the vibration of an object in a material medium.
• 📣 A loudspeaker is an electro-acoustic converter that uses magnets, a coil, and an elastic membrane to convert electrical signals into sound waves.
• 🎙️ A microphone is an acousto-electric converter that converts sound vibrations into electrical signals, with components similar to a loudspeaker.
• 👂 The human ear is a complex sound receiver with three main parts: the external ear, the middle ear with the eardrum and ossicles, and the internal ear with the cochlea.
• 🎵 Sound waves received by the ear are transformed into nerve messages as electric signals, which are then processed by the brain.
• 🚫 The human ear can hear sounds within the frequency range of 20 Hz to 20 kHz, known as audible frequencies.
• 🔉 Sounds below 20 Hz are called infrasounds, and those above 20 kHz are called ultrasounds, which are inaudible to the human ear.
• 🏊 Ultrasounds have practical applications in echolocation, such as in sonar technology used for depth measurement and object detection underwater.
• 🌊 Echo sonar works on the principle of sending ultrasonic waves and measuring the time it takes for their echo to return, allowing for the calculation of distances.
• ⏱️ The depth of water can be determined using the speed of sound in water and the time interval between the emission and reception of an ultrasound's echo.

Q & A

What is the main topic of the lesson described in the transcript?

The main topic of the lesson is the reception of sound, focusing on how sound is received and converted into electrical signals by devices like microphones and the human ear.

What are the main parts of an electrodynamic loudspeaker?

The main parts of an electrodynamic loudspeaker are magnets, a coil, and an elastic membrane.

How does a loudspeaker function when connected to an AC source?

When connected to an AC source, an electromagnetic force is created in the loudspeaker, causing the coil to vibrate. This vibration is transferred to the elastic membrane, which then emits sound waves.

What is the speed of sound in solids, and why is it relevant?

Sound is fastest in solids because it is a mechanical wave that requires a medium to propagate. The speed of sound in solids is not explicitly mentioned in the transcript, but it is generally faster than in liquids or gases.

What is a microphone and how does it relate to the concept of an electro-acoustic converter?

A microphone is a sound receiver that converts sound vibrations into electrical signals, making it an acousto-electric converter. It is related to the concept of an electro-acoustic converter because it transforms acoustic energy into electrical energy.

What are the main parts of a microphone?

The main parts of a microphone are the elastic membrane, the coil, and the magnet.

How does a microphone convert sound vibrations into electrical signals?

A sound wave causes the elastic membrane of the microphone to vibrate. This vibration is transferred to the coil, which moves within the magnetic field, inducing an electrical current due to electromagnetic induction.

What are the three main parts of the human ear?

The three main parts of the human ear are the external ear, the middle ear, and the internal ear.

How does the human ear process sound waves?

Sound waves are received by the external ear, causing vibrations that are transmitted to the eardrum and then to the ossicles in the middle ear. These vibrations are then sent to the internal ear, where auditory cells convert them into nerve messages as electric signals.

What is the range of audible frequencies for the human ear?

The human ear can hear frequencies between 20 hertz and 20 kilohertz (20,000 Hz).

What are the three regions of the audible frequency range?

The audible frequency range is divided into deep sounds (20 to 500 Hz), medium sounds (500 to 3,000 Hz), and sharp sounds (3,000 to 20,000 Hz).

What is the principle behind the use of sonar, and how is it applied?

The principle behind sonar is the reflection of ultrasounds. It is applied by sending a burst of ultrasonic waves towards a surface and measuring the time it takes for the echo to return. The depth or distance can be calculated using the speed of sound and the time interval.

How is the depth of water measured using sonar in the example provided?

In the example, a sonar emits an ultrasound and receives its echo after 400 milliseconds. Using the formula v = (2d)/(∆t), where v is the speed of sound in water (1500 meters per second), the depth d is calculated to be 300 meters.

Outlines

00:00

🔊 Understanding Sound Reception and Loudspeakers

This section delves into the reception of sound, following the study of sound emission. It explains that sound is a longitudinal mechanical wave generated by object vibrations. The main components of a loudspeaker are identified as magnets, a coil, and an elastic membrane, which together convert electrical signals into sound waves. The speed of sound varies with the medium, being fastest in solids. The objectives include explaining the operation of a microphone and the range of audible frequencies for the human ear. A microphone, an acousto-electric converter, is described as having an elastic membrane, a coil, and a magnet, similar to a loudspeaker, but it converts sound vibrations into electrical signals through electromagnetic induction. The human ear, a superior sound receiver, is anatomically and functionally described, highlighting its ability to convert sound vibrations into nerve impulses. The audible frequency range for humans is detailed, with infrasound and ultrasound defined as non-audible sounds below and above this range, respectively.

05:00

🛰 Applications of Ultrasound in Sonar and Echolocation

This part explores the practical applications of ultrasound, particularly in echolocation and sonar technology. It discusses how sonar works by sending ultrasonic waves and measuring the time it takes for the echo to return, allowing for the calculation of distances such as the depth of water. The principle of sonar is explained through the formula relating wave speed to the time interval between emission and reception of the wave. An example calculation is provided, where a sonar emits an ultrasound and receives its echo after a certain time, leading to the determination of water depth. The section concludes with a summary of the chapter's content and a thank you note to viewers.

Keywords

💡Emission of Sound

Emission of sound refers to the process by which sound is produced and radiated into the surrounding environment. In the context of the video, it is mentioned in the introduction as a precursor to the main topic of the lesson, which is the reception of sound. The script explains that sound is produced by the vibration of an object in a material medium, which is a fundamental concept for understanding how sound is both emitted and received.

💡Reception of Sound

Reception of sound is the process by which sound waves are detected and interpreted by a receiver, such as the human ear or a microphone. The video focuses on this concept in part 2, explaining how microphones and ears convert sound vibrations into electrical signals or nerve impulses, respectively. This is central to the video's theme as it delves into the mechanisms of sound detection.

💡Longitudinal Mechanical Wave

A longitudinal mechanical wave is a type of wave, like sound, where the particle motion is parallel to the direction of wave propagation. The video script mentions that sound is a longitudinal mechanical wave, emphasizing that it requires a material medium to travel through, which is a key aspect of how sound is both emitted and received.

💡Electrodynamic Loudspeaker

An electrodynamic loudspeaker is a device that converts electrical signals into sound. The script describes its main parts as magnets, a coil, and an elastic membrane. The functioning of a loudspeaker is tied to the video's theme as it demonstrates the conversion of electrical energy into mechanical vibrations, which are then emitted as sound waves.

💡Electroacoustic Converter

An electroacoustic converter is a device that changes electrical energy into acoustic energy or vice versa. The video mentions that a loudspeaker is an example of an electroacoustic converter, highlighting the process where an AC source creates an electromagnetic force that leads to the vibration of the coil and membrane, resulting in sound emission.

💡Microphone

A microphone is a sound receiver that converts sound vibrations into electrical signals. The video explains that it is an acoustoelectric converter, with main parts similar to those of a loudspeaker. The script describes how a sound wave causes the elastic membrane of the microphone to vibrate, which in turn induces an electric current in the coil due to electromagnetic induction.

💡Audible Frequencies

Audible frequencies are the range of frequencies that the human ear can hear, which is between 20 Hz and 20 kHz. The video script specifies this range and explains that sounds outside this range are inaudible to humans, categorizing them as infrasounds (below 20 Hz) or ultrasounds (above 20 kHz). This concept is crucial for understanding the limitations of human hearing and the capabilities of sound-detecting devices.

💡Human Ear

The human ear is the organ of hearing and is described in the video as an unmatched sound receiver. It consists of the external ear, middle ear, and internal ear. The video script details how sound waves are received and transformed into nerve messages as electric signals, which is a fundamental process for the reception of sound and a key part of the video's educational content.

💡Echolocation

Echolocation is a biological and technological method of navigation and detection through the use of reflected sound waves or echoes. The video script discusses the use of echolocation in sonar technology, which is a practical application of the reflection of ultrasounds. This concept is related to the video's theme as it shows an advanced use of sound wave reception for various practical purposes.

💡Sonar

Sonar, or sound navigation and ranging, is a technique that uses the echo of ultrasounds to determine the distance, depth, or presence of objects. The video script provides an example of how sonar is used to measure the depth of water, illustrating the practical application of the principles of sound reception and echolocation in maritime navigation and exploration.

Highlights

Sound is a longitudinal mechanical wave produced by the vibration of an object.

The main parts of an electrodynamic loudspeaker are magnets, coil, and elastic membrane.

A loudspeaker is an electro-acoustic converter that converts electrical signals into sound.

The speed of sound varies depending on the medium and is fastest in solids.

A microphone is an acousto-electric converter that converts sound vibrations into electrical signals.

The main parts of a microphone are the elastic membrane, coil, and magnet.

Sound waves cause the elastic membrane of a microphone to vibrate, inducing an electric current.

The human ear is a sound receiver that is unmatched by any microphone.

The ear consists of the external ear, middle ear, and internal ear.

Sound waves received by the ear are transmitted as nerve messages as electric signals.

The human ear can hear frequencies between 20 Hz and 20 kHz.

Sounds with frequencies below 20 Hz are called infrasounds, and above 20 kHz are called ultrasounds.

The audible frequency range is divided into deep, medium, and sharp sounds.

Ultrasounds are used in echo sonar for determining the depth of the sea or detecting submarines.

Ecography is a medical technique using ultrasounds to obtain images of body organs.

Echo is used in exploration of fossils, patrol, and geology for searching oil and gas.

The principle of a sonar is based on the reflection of ultrasounds and measuring the time interval between emission and reception.

The depth of water can be determined using the speed of ultrasound and the time interval between emission and reception of its echo.

Transcripts

[Music]

in the first part of this lesson we have

studied about emission of sound today in

part 2 we are going to learn more about

reception of sound

but first let's remember

sound is a longitudinal mechanical wave

produced by the vibration of an object

in a material medium

the main parts of an electrodynamic

loudspeaker are magnets coil and elastic

membrane

a loudspeaker is an electro acoustic

converter what about the functioning of

a loudspeaker

when an ac source is connected to the

loudspeaker then an electromagnetic

force is created causing the vibration

of the coil

being connected to the coil the membrane

also undergoes vibrations that lead to

the emission of the sound waves

the speed of sound depends on the medium

of propagation and sound is fastest in

solids since it is a mechanical wave

the objectives of this part are

explain how a microphone works and

indicate the range of audible sounds

heard by the human ear

now let's start with part 2 reception of

sound

one of the most popular receivers of

sound is the microphone it is a sound

receiver that converts the sound

vibrations detected into electrical

signals

therefore it is called an acousto

electric converter

before explaining the functioning of the

microphone it's important to list its

main parts which are the elastic

membrane the coil and the magnet

these parts are common between the lock

speaker and the microphone

now let's see how do these parts

interfere and the functioning of the

microphone a sound wave transmitted by

air particles sets the elastic membrane

of the microphone in vibration

the membrane vibrates with the same

frequency as the wave

being fixed to the membrane the coil

vibrates between the poles of the magnet

and the current is induced

due a phenomena which is called the

electromagnetic induction

therefore sound vibrations received by

the membrane are then transformed into

electric signals the ear the organ of

hearing is a sound receiver which is

unmatchable by any microphone

is there an analogy between the

operation of these two receivers the ear

has three main parts the external ear

formed of the article

which leads to the auditory canal

the middle ear separated from the

external ear by the eardrum and is

formed of three small movable bones

called the ossicles

the internal ear formed of the cochlea

covered with the auditory cells

how does it function sound waves are

received by the article of the ear where

they produce vibrations these vibrations

are transmitted to the eardrum and then

to the ossicles of the middle ear which

transmits them to the internal ear the

auditory cells of the internal ear

transmit these vibrations in a nerve

message as electric signals

the ear is sensitive to a limited range

of frequencies called audible

frequencies

the human ear can hear a sound of a

frequencies between 20 hertz and 20

kilohertz or 20 000 shirts

the non-audible sounds are called

infrasounds after frequency is less than

20 hertz and they are called ultrasounds

if their frequencies are greater than 20

000 hertz

these sounds having these frequencies

are not heard by a human ear

the audible frequency range is divided

into three regions

first

the frequencies ranging between 20 and

500 hertz are called deep sounds those

between 500 and 3000 hertz are called

medium sounds

and

between three thousands and twenty

thousand hertz are called sharp sounds

one of the most popular and useful

applications of ultrasounds is the echo

sonar which is a technique based on the

echo of ultrasound some applications of

the echo are zoner is a device used in

ships to determine the depth of the sea

or to detect a submarine

the ecography

is a medical technique used to obtain

images of certain organs of the body it

is done without any pain and without

danger

exploration of fossils or patrol

and geology the echo is used in the

search for oil and gas

let's explain the principle of a soner

a zoner is a practical application of

reflection of ultrasounds

its principle is to send a salvo of

ultrasonic waves to the surface to be

studied and then to measure the time

delta t between the emission of these

waves and the reception of its echo

the speed of these waves is equal to the

distance traveled during emission and

reception divided by the time from the

instant of emission to that of reception

and since the distance covered by the

wave is the same distance covered by its

echo then we can say that the speed v is

equal to 2d divided by delta t which is

the time interval between emission and

reception

where the speed v is equal to 1 500

meter per second which is the speed of

sound in the water

let's have a direct application on this

owner

a sonar emits an ultrasound of speed

1500 meter per seconds down a c and

receives its echo after 400 milliseconds

determine the depth of the water at this

toner position

please try to solve this application

first alone then check the solution with

me

the speed is given by the distance

traveled by this wave and its echo

divided by the time interval between the

emission and the reception then it is

equal to 2d divided by delta t

by substitution we will get that the

distance d is equal to 300 meters

therefore the depth of the water is

equal to 300 meters

[Music]

it's the end of this chapter thank you

for watching

[Music]