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.